bluuebunny/crossref_metadata_2025 huggingface dataset:
GM1 ganglioside: another nuclear lipid that modulates nuclear calcium. GM1 potentiates the nuclear sodium–calcium exchangerThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell.
Authors: Ledeen Robert W. , Wu Gusheng
Published: August 2006

The nuclear envelope (NE) enclosing the cell nucleus, although morphologically and chemically distinct from the plasma membrane, has certain features in common with the latter including the presence of GM1 as an important modulatory molecule. This ganglioside influences Ca2+flux across both membranes, but by quite different mechanisms. GM1 in the NE contributes to regulation of nuclear Ca2+through potentiation of a Na+/Ca2+exchanger in the inner nuclear membrane, whereas in the cell membrane, it regulates cytosolic Ca2+through modulation of a nonvoltage-gated Ca2+channel. Studies with neuroblastoma cells suggest GM1 concentration becomes elevated in the NE with onset of axonogenesis. However, the nuclear GM1/exchanger complex is not limited to neuronal cells but also occurs in NE of astrocytes, C6 cells, and certain non-neural cells. Immunoprecipitation and immunoblot experiments have shown high affinity association of the nuclear Na+/Ca2+exchanger with GM1, in contrast to Na+/Ca2+exchangers of the plasma membrane, which bind GM1 less avidly or not at all. This is believed to be due to different isoforms of the exchanger and a difference in topology of GM1 relative to the large inner loop of the exchanger in the 2 membranes. Cultured neurons from mice genetically engineered to lack GM1 suffered Ca2+dysregulation as seen in their high vulnerability to Ca2+-induced apoptosis. They were rescued by GM1 and more effectively by LIGA20, a membrane-permeant derivative of GM1. The mutant animals were highly susceptible to kainate-induced seizures, which are also a reflection of Ca2+dysregulation. The seizures were effectively attenuated by LIGA20 in parallel with the ability of this agent to enter brain cells, insert into the NE, and potentiate Na+/Ca2+exchange activity in the nucleus. The Na+/Ca2+exchanger of the NE, in association with nuclear GM1, is thus seen contributing to independent regulation of Ca2+by the nucleus in a manner that provides cytoprotection against Ca2+-induced apoptosis.
High resolution analysis of mammalian nuclear structure throughout the cell cycle: implications for nuclear pore complex assembly during interphase and mitosisThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell.
Authors: Drummond Sheona P. , Rutherford Sandra A. , Sanderson Helen S. , Allen Terry D.
Published: August 2006

Nuclear pore complexes (NPCs) are the gateways for both active and passive bidirectional molecular transport between the nucleoplasm and cytoplasm. These mega-dalton assemblies are composed of multiple copies of approximately 30 distinct proteins termed nucleoporins. Higher eukaryotes display an “open” mitosis in which the NPCs, nuclear envelope, and lamina disassemble. During mitosis several nucleoporins are redistributed to kinetochores until they are recruited back to the periphery of chromatin as the NPCs are reassembled. Within this study we have developed and optimized the visualization of mammalian cells and their chromosome profiles throughout the cell-cycle. Close attention has been paid to the preservation of chromatin, membranes, and NPC structure to investigate the ultrastructural locations of specific proteins in both interphase and mitosis.
G-protein-coupled receptors, channels, and Na+–H+exchanger in nuclear membranes of heart, hepatic, vascular endothelial, and smooth muscle cellsThis paper is one of a selection of papers published in this Special Issue, entitled The Nucleus: A Cell Within A Cell.
Authors: Bkaily Ghassan , Nader Moni , Avedanian Levon , Choufani Sana , Jacques Danielle , D’Orléans-Juste Pedro , Gobeil Fernand , Chemtob Sylvain , Al-Khoury Johny
Published: August 2006

The action of several peptides and drugs is thought to be primarily dependent on their interactions with specific cell surface G-protein-coupled receptors and ionic transporters such as channels and exchangers. Recent development of 3-D confocal microscopy allowed several laboratories, including ours, to identify and study the localization of receptors, channels, and exchangers at the transcellular level of several cell types. Using this technique, we demonstrated in the nuclei of several types of cells the presence of Ca2+channels as well as Na+–H+exchanger and receptors such as endothelin-1 and angiotensin II receptors. Stimulation of these nuclear membrane G-protein-coupled receptors induced an increase of nuclear Ca2+. Our results suggest that, similar to the plasma membrane, nuclear membranes possess channels, exchangers and receptors such as those for endothelin-1 and angiotensin II, and that the nucleus seems to be a cell within a cell. This article will emphasize these findings.
QUANTUM ELECTRODYNAMICS AND CHROMODYNAMICS TREATED THROUGH THOMPSON'S APPROACH
Authors: NASSIF CLÁUDIO , SILVA P. R.
Published: August 2006

In this work we apply Thompson's method (of the dimensions and scales) to study some features of the Quantum Electrodynamics and Chromodynamics. This heuristic method can be considered as a simple and alternative way to the Renormalization Group approach and when applied to QED-Lagrangian is able to obtain in a first approximation both the running coupling constant behavior of α(μ) and the mass m(μ). The calculations are evaluated only at dc = 4, where dc is the upper critical dimension of the problem, so that we obtain the logarithmic behavior both for the coupling α and the excess of mass Δm on the energy scale μ. Although our results are well known in the vast literature of field theories, the advantage of Thompson's method, beyond its simplicity is that it is able to extract directly from QED-Lagrangian the physical (finite) behavior of α(μ) and m(μ), bypassing hard problems of divergences which normally appear in the conventional renormalization schemes applied to field theories like QED. Quantum Chromodynamics (QCD) is also treated by the present method in order to obtain the quark condensate value. Besides this, the method is also able to evaluate the vacuum pressure at the boundary of the nucleon. This is done by assumming a step function behavior for the running coupling constant of the QCD, which fits nicely to some quantities related to the strong interaction evaluated through the MIT-bag model.
STUDIES OF THE FEW-BODY PROBLEM IN ATOMIC BREAK-UP PROCESSES
Authors: SCHULZ M. , MADISON D. H.
Published: August 2006

Fully differential studies of single ionization of neutral atoms by charged particle impact have proven to be extremely powerful to advance our understanding of the few-body dynamics in atomic processes. Until a few years ago, such data were only available for electron impact and were mostly limited to electrons ejected into the scattering plane. When fully differential data were finally obtained for ion impact covering the entire three-dimensional space, very surprising features were observed. It then became clear that our understanding of ionization processes in atomic collisions is not nearly as complete as previously assumed. Here, we review the development of experimental and theoretical studies of three-dimensional fully differential single ionization cross-sections since then.
THE CHANGING IMPORTANCE OF THE STRENGTH OF TIES THROUGHOUT THE ENTREPRENEURIAL PROCESS
Authors: EVALD MAJBRITT ROSTGAARD , KLYVER KIM , SVENDSEN SUSANNE GREN
Published: August 2006

In this paper we review selected papers on entrepreneurship dealing with Granovetter's concept of strong and weak ties in order to systematically organize the articles according to the researchers' estimate of what ties are most important.

The aim is to find out what the existing research applying the entrepreneurship network approach says about the changing importance of strong and weak ties in different phases of the entrepreneurial process. Thus we investigate how different types of strong and weak ties change in importance according to, which phases of the entrepreneurial process the entrepreneurial act takes place within. Based on these findings, we develop a conceptual framework showing that strong ties, like family, friends and close business contacts, seem to play an important role in the emergence phase. Whereas in the phase of the newly established firm, a mix of strong and weak ties, including new and former business contacts as well as family and friends, seems to play an important role. Furthermore, in the phase of the mature firm a mix of strong and weak ties seem to play the most important role, although the composition of what constitutes this mix is different from the former phase. In the last phase, the mix of strong and weak ties includes special and close business contacts and one-shot deal business contacts. Accordingly, we have identified the changing importance of the strength of ties throughout the entrepreneurial process.
IMPACTS OF DIVERSIFICATION AND CORPORATE ENTREPRENEURSHIP STRATEGY MAKING ON GROWTH AND PROFITABILITY: A NORMATIVE MODEL
Authors: ANTONCIC BOSTJAN
Published: August 2006

Diversification strategy is an important driver of organizational conduct and performance. Despite its recognized linkage to other strategy-making elements, such as corporate entrepreneurship, research has devoted minimal attention to explicitly investigating relationships among diversification, corporate entrepreneurship and performance elements. This study contributes to a better understanding of diversification strategy driven corporate entrepreneurship and performance by testing a normative model on a sample of 449 Slovenian firms. The findings demonstrate that single business and vertical diversification make some difference in organizational growth and profitability in terms of their direct effects, but not indirectly with the mediation of corporate entrepreneurship strategy-making elements, which can be independently of diversification important for performance improvement.
STOCHASTIC POST-BUCKLING OF FRAMES USING KOITER'S METHOD
Authors: SCHAFER B. W. , GRAHAM-BRADY L.
Published: August 2006

The objective of this paper is to explore the impact of stochastic inputs on the buckling and post-buckling response of structural frames. In particular, we examine the impact of random member stiffness on the buckling load, and the initial slope and curvature of the post-buckling response of three example frames. A finite element implementation of Koiter's perturbation method is employed to efficiently examine the post-buckling response. Monte Carlo simulations where the member stiffness is treated as a random variable, as well as correlated and uncorrelated random fields, are completed. The efficiency of Koiter's perturbation method is the key to the feasibility of applying Monte Carlo simulation techniques, which typically requires a large number of sample simulations. In an attempt to curtail the need for multiple sample calculations, an alternative first-order perturbation expansion is proposed for approximating the mean and variance of the post-buckling behavior. However, the limitations of this first-order perturbation approximation are demonstrated to be significant. The simulations indicate that deterministic characteristics of the post-buckling response can be inadequate in the face of input randomness. In one case, a frame that is stable symmetric in the deterministic case is found to be asymmetric when randomness in the input is incorporated; therefore, this frame has real potential for imperfection sensitivity. The importance of random field models for the member stiffness as opposed to random variable models is highlighted. The simulations indicate that the post-buckling response can magnify input randomness, as variability in the post-buckling parameters can be greater than the variability in the input parameters.
VIBRATIONS AND STABILITY OF COLUMNS LOADED BY THREE SIDE SURFACES OF CIRCULAR CYLINDERS CONSIDERING TYPE OF FRICTION IN LOADING HEADS
Authors: TOMSKI L. , PODGÓRSKA-BRZDȨKIEWICZ I.
Published: August 2006

This paper presents the new type of head loading the columns, comprising of elements making a side surface of circular cylinders. It demonstrates a constructional solution of forcing and receiving heads, as well as theoretical considerations related to the determination of boundary conditions, taking into account the loading of needle rolling bearings or rigid elements in the loading heads. Results of experimental investigations of the free vibration of columns having various constructions of receiving heads were presented. In the case of columns for which rigid elements were installed in the receiving heads, the rigidity of equivalent rotational spring is determined, which takes into account the rigidity of the free end of the column caused by sliding friction existing in the loading head elements. The value of critical force and the course of the natural frequency against external load for given geometry and physical constants of the column are determined.
DYNAMIC RESPONSES OF A TWO-SPAN BEAM SUBJECTED TO HIGH SPEED 2DOF SPRUNG VEHICLES
Authors: SEETAPAN PRITSATHAT , CHUCHEEPSAKUL SOMCHAI
Published: August 2006

The deflection, bending moment, shear force and acceleration-time histories of a two-span beam subjected to moving sprung vehicles are presented. The vehicle model is a 2DOF system with a constant velocity. The two-span beam with a rough surface is used as structure model. The beam is defined in modal domain by natural frequencies, mode shapes and modal damping values. The rough surface is modeled by filtered white noise. The equations of motion for the coupled vehicle-structure system are formulated, for non-dimensionalized variables in the system equation. The first-order linear stochastic differential equations are solved, and the effects of the span passage rate and other important parameters are studied.
FREE VIBRATION OF TRANSVERSELY ISOTROPIC SOLID AND THICK-WALLED TOROIDAL SHELLS
Authors: LIU YAN JANE , BUCHANAN GEORGE R.
Published: August 2006

The frequency of vibration of thick-walled toroidal shells is studied using a finite element formulation wherein the finite element is derived directly in toroidal coordinates. Hexagonal crystals of thallium and cadmium are used as representative transversely isotropic materials. The shell is assumed to be transversely isotropic with respect to the toroidal radial direction, and results based on that assumption are contrasted to a shell that is transversely isotropic with respect to the circumferential toroidal coordinate. It is established that an analysis based on a toroidal coordinate system is superior to an axisymmetric coordinate system and has some advantages over a commercial finite element code. Tables of results are presented that compare frequency of vibration for the above mentioned transversely isotropic materials and isotropic materials.
Stem Cells and Chronic Lung Disease
Authors: Gomperts Brigitte N. , Strieter Robert M.
Published: August 2006

Stem cells have been shown to contribute to the repair and regeneration of injured lungs. These stem cells are resident in specific protected niches in the lung, or they can be mobilized from the bone marrow and recruited from the circulation in the setting of severe injury. Normal repair of the airway involves regeneration of the airway epithelium by stem cells in both the proximal airway and distal airspace, whereas aberrant repair of the lung may result from stem cells that lead to fibrosis. The stem cell niche in the lung is probably critical in determining whether “good” or “bad” stem cells are involved in local repair, and therefore whether fibrosis predominates. There is much excitement about the possibility of harnessing stem cells for repair and regeneration of the lungs. This review highlights current knowledge of this area and identifies gaps in our understanding of this complicated process.
Inhibition of Gαq-dependent PLC-β1 activity by PKG and PKA is mediated by phosphorylation of RGS4 and GRK2
Authors: Huang Jiean , Zhou Huiping , Mahavadi Sunila , Sriwai Wimolpak , Murthy Karnam S.
Published: August 2006

In smooth muscle of the gut, Gq-coupled receptor agonists activate preferentially PLC-β1 to stimulate phosphoinositide (PI) hydrolysis and inositol 1,4,5-trisphosphate (IP3) generation and induce IP3-dependent Ca2+ release. Inhibition of Ca2+ mobilization by cAMP- (PKA) and cGMP-dependent (PKG) protein kinases reflects inhibition of PI hydrolysis by both kinases and PKG-specific inhibitory phosphorylation of IP3 receptor type I. The mechanism of inhibition of PLC-β1-dependent PI hydrolysis has not been established. Neither Gq nor PLC-β1 was directly phosphorylated by PKA or PKG in gastric smooth muscle cells. However, both kinases 1) phosphorylated regulator of G protein signaling 4 (RGS4) and induced its translocation from cytosol to plasma membrane, 2) enhanced ACh-stimulated association of RGS4 and Gαq·GTP and intrinsic Gαq·GTPase activity, and 3) inhibited ACh-stimulated PI hydrolysis. RGS4 phosphorylation and inhibition of PI hydrolysis were blocked by selective PKA and PKG inhibitors. Expression of RGS4(S52A), which lacks a PKA/PKG phosphorylation site, blocked the increase in GTPase activity and the decrease in PI hydrolysis induced by PKA and PKG. Blockade of PKA-dependent effects was only partial. Selective phosphorylation of G protein-coupled receptor kinase 2 (GRK2), which contains a RGS domain, by PKA augmented ACh-stimulated GRK2:Gαq·GTP association; both effects were blocked in cells expressing GRK2(S685A), which lacks a PKA phosphorylation site. Inhibition of PI hydrolysis induced by PKA was partly blocked in cells expressing GRK2(S685A) and completely blocked in cells coexpressing GRK2(S685A) and RGS4(S52A) or Gαq(G188S), a Gαq mutant that binds GRK2 but not RGS4. The results demonstrate that inhibition of PLC-β1-dependent PI hydrolysis by PKA is mediated via stimulatory phosphorylation of RGS4 and GRK2, leading to rapid inactivation of Gαq·GTP. PKG acts only via phosphorylation of RGS4.
Building the power house: recent advances in mitochondrial studies through proteomics and systems biology
Authors: Vo Thuy D. , Palsson Bernhard O.
Published: August 2006

The emerging field of systems biology seeks to develop novel approaches to integrate heterogeneous data sources for effective analysis of complex living systems. Systemic studies of mitochondria have generated a large number of proteomic data sets in numerous species, including yeast, plant, mouse, rat, and human. Beyond component identification, mitochondrial proteomics is recognized as a powerful tool for diagnosing and characterizing complex diseases associated with these organelles. Various proteomic techniques for isolation and purification of proteins have been developed; each tailored to preserve protein properties relevant to study of a particular disease type. Examples of such techniques include immunocapture, which minimizes loss of posttranslational modification, 4-iodobutyltriphenylphosphonium labeling, which quantifies protein redox states, and surface-enhanced laser desorption ionization-time-of-flight mass spectrometry, which allows sequence-specific binding. With the rapidly increasing number of discovered molecular components, computational models are also being developed to facilitate the organization and analysis of such data. Computational models of mitochondria have been accomplished with top-down and bottom-up approaches and have been steadily improved in size and scope. Results from top-down methods tend to be more qualitative but are unbiased by prior knowledge about the system. Bottom-up methods often require the incorporation of a large amount of existing data but provide more rigorous and quantitative information, which can be used as hypotheses for subsequent experimental studies. Successes and limitations of the studies reviewed here provide opportunities and challenges that must be addressed to facilitate the application of systems biology to larger systems.
Statin-induced apoptosis and skeletal myopathy
Authors: Dirks Amie J. , Jones Kimberly M.
Published: August 2006

Over 100 million prescriptions were filled for statins (3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors) in 2004. Statins were originally developed to lower plasma cholesterol in patients with hypercholesterolemia and are the most effective drugs on the market in doing so. Because of the discovered pleiotropic effects of statins, the use has expanded to the treatment of many other conditions, including ventricular arrythmias, idiopathic dilated cardiomyopathy, cancer, osteoporosis, and diabetes. The elderly population is growing. Therefore, it is estimated that the number of statin users will also increase. Fortunately, the use of statins is relatively safe with few side effects. Myopathy is the most common side effect with symptoms ranging from fatigue, weakness, and pain to symptoms associated with rhabdomyolysis which is a life-threatening condition. The development of statin-induced rhabdomyolysis is rare occurring in ∼0.1% of patients; however, the occurrence of less severe symptoms is underreported and may be 1–5% or more. Physical exercise appears to increase the likelihood for the development of myopathy in patients taking statins. It is thought that as many as 25% of statin users who exercise may experience muscle fatigue, weakness, aches, and cramping due to statin therapy and potentially dismissed by the patient and physician. The mechanisms causing statin-induced myopathy have not been elucidated; however, research efforts suggest that apoptosis of myofibers may contribute. The mitochondrion is considered a regulatory center of apoptosis, and therefore its role in the induction of apoptosis will be discussed as well as the mechanism of statin-induced apoptosis and myopathy.
Mitochondrial transport in processes of cortical neurons is independent of intracellular calcium
Authors: Beltran-Parrazal Luis , López-Valdés Héctor E. , Brennan K. C. , Díaz-Muñoz Mauricio , de Vellis Jean , Charles Andrew C.
Published: August 2006

Mitochondria show extensive movement along neuronal processes, but the mechanisms and function of this movement are not clearly understood. We have used high-resolution confocal microscopy to simultaneously monitor movement of mitochondria and changes in intracellular [Ca2+] ([Ca2+]i) in rat cortical neurons. A significant percentage (27%) of the total mitochondria in cortical neuronal processes showed movement over distances of >2 μM. The average velocity was 0.52 μm/s. The velocity, direction, and pattern of mitochondrial movement were not affected by transient increases in [Ca2+]i associated with spontaneous firing of action potentials. Stimulation of Ca2+ transients with forskolin (10 μM) or bicuculline (10 μM), or sustained elevations of [Ca2+]i evoked by glutamate (10 μM) also had no effect on mitochondrial transit. Neither removal of extracellular Ca2+, depletion of intracellular Ca2+ stores with thapsigargin, or inhibition of synaptic activity with TTX (1 μM) or a cocktail of CNQX (10 μM) and MK801 (10 μM) affected mitochondrial movement. These results indicate that movement of mitochondria along processes is a fundamental activity in neurons that occurs independently of physiological changes in [Ca2+]i associated with action potential firing, synaptic activity, or release of Ca2+ from intracellular stores.
Nitric oxide regulation of mitochondrial oxygen consumption I: cellular physiology
Authors: Giulivi Cecilia , Kato Kazunobu , Cooper Christopher Eric
Published: August 2006

Mitochondrial biochemistry is complex, expanding from oxygen consumption, oxidative phosphorylation, lipid catabolism, heme biosynthesis, to apoptosis, calcium homeostasis, and production of reactive oxygen species, including nitric oxide (NO). The latter molecule is produced by a mitochondrial NO synthase (mtNOS). The rates of consumption and production determine the steady-state concentration of NO at subcellular levels, leading to regulation of mitochondrial events. Temporospatial processes tightly regulate production of NO in mitochondria to maximize target effects and minimize deleterious reactions. Temporal regulatory mechanisms of mtNOS include activation by calcium signaling and transcriptional/translational regulations. Calcium-activated mtNOS inhibits mitochondrial respiration, resulting in a decrease of the oxygen consumption. This negative regulation antagonizes the effects of calcium on calcium-dependent dehydrogenases in the citric acid cycle, preventing the formation of anoxic foci. Temporal regulation of NO production by intracellular calcium signaling is a complex process, considering the heterogeneous intracellular calcium response and distribution. NO production in mitochondria is spatially regulated by mechanisms that determine subcellular localization of mtNOS, likely acylation and protein-protein interactions, in addition to transcriptional regulation as neuronal NOS. Because NO rapidly decays in mitochondria, subcellular localization of mtNOS is crucial for NO to function as a signal molecule. These temporospatial processes are biologically important to allow NO to act as an effective signal molecule to regulate mitochondrial events such as oxygen consumption and reactive oxygen species production.
Regulation of myostatin expression and myoblast differentiation by FoxO and SMAD transcription factors
Authors: Allen David L. , Unterman Terry G.
Published: August 2006

Myostatin, a member of the transforming growth factor (TGF)-β family, plays an important role in regulating skeletal muscle growth and differentiation. Here we examined the role of FoxO1 and SMAD transcription factors in regulating myostatin gene expression and myoblast differentiation in C2C12 myotubes in vitro. Both myostatin and FoxO1 mRNA expression were greater in fast- vs. slow-twitch skeletal muscles in vivo. Moreover, expression of a constitutively active form of FoxO1 increased myostatin mRNA and increased activity of a myostatin promoter reporter construct in differentiated C2C12 myotubes. Mutagenesis of highly conserved FoxO or SMAD binding sites significantly decreased myostatin promoter activity, and binding assays showed that both FoxO1 and SMADs bind to their respective sites in the myostatin promoter. Treatment with TGF-β and/or overexpression of SMAD2, -3, or -4 also resulted in a significant increase in myostatin promoter activity. Treatment with TGF-β along with overexpression of SMAD2 and FoxO1 resulted in the largest increase in myostatin promoter activity. Finally, TGF-β treatment and SMAD2 overexpression greatly potentiated FoxO1-mediated suppression of myoblast differentiation. Together these data demonstrate that FoxO1 and SMAD transcription factors regulate the expression of myostatin and contribute to the control of muscle cell growth and differentiation.
Apical electrolyte concentration modulates barrier function and tight junction protein localization in bovine mammary epithelium
Authors: Quesnell Rebecca R. , Erickson Jamie , Schultz Bruce D.
Published: August 2006

In vitro mammary epithelial cell models typically fail to form a consistently tight barrier that can effectively separate blood from milk. Our hypothesis was that mammary epithelial barrier function would be affected by changes in luminal ion concentration and inflammatory cytokines. Bovine mammary epithelial (BME-UV cell line) cells were grown to confluence on permeable supports with a standard basolateral medium and either high-electrolyte (H-elec) or low-electrolyte (L-elec) apical medium for 14 days. Apical media were changed to/from H-elec medium at predetermined times prior to assay. Transepithelial electrical resistance ( Rte) was highest in monolayers continuously exposed to apical L-elec. A time-dependent decline in Rte began within 24 h of H-elec medium exposure. Change from H-elec medium to L-elec medium time-dependently increased Rte. Permeation by FITC-conjugated dextran was elevated across monolayers exposed to H-elec, suggesting compromise of a paracellular pathway. Significant alteration in occludin distribution was evident, concomitant with the changes in Rte, although total occludin was unchanged. Neither substitution of Na+ with N-methyl-d-glucosamine (NMDG+) nor pharmacological inhibition of transcellular Na+ transport pathways abrogated the effects of apical H-elec medium on Rte. Tumor necrosis factor alpha, but not interleukin-1β nor interleukin-6, in the apical compartment caused a significant decrease in Rte within 8 h. These results indicate that mammary epithelium is a dynamic barrier whose cell-cell contacts are acutely modulated by cytokines and luminal electrolyte environment. Results not only demonstrate that BME-UV cells are a model system representative of mammary epithelium but also provide critical information that can be applied to other mammary model systems to improve their physiological relevance.
Sympathetic but not sensory denervation stimulates white adipocyte proliferation
Authors: Foster Michelle T. , Bartness Timothy J.
Published: August 2006

White adipocyte proliferation is a hallmark of obesity, but it largely remains a mechanistic mystery. We and others previously demonstrated that surgical denervation of white adipose tissue (WAT) triggers increases in fat cell number, but it is unknown whether this was due to preadipocyte proliferation or maturation of existing preadipocytes that allowed them to be counted. In addition, surgical denervation severs not only sympathetic but also sensory innervation of WAT. Therefore, we tested whether sympathetic WAT denervation triggers adipocyte proliferation using 5-bromo-2′-deoxyuridine (BrdU) as a marker of proliferation and quantified BrdU-immunoreactive (ir) cells that were colabeled with AD-3-ir, an adipocyte-specific membrane protein marker. The unilateral denervation model was used for all experiments where Siberian hamster inguinal WAT (IWAT) was unilaterally denervated, the contralateral pad was sham denervated serving as a within-animal control, and then BrdU was injected systemically for 6 days. When IWAT was surgically denervated, severing both sympathetic and sensory nerves, tyrosine hydroxylase (TH)-ir, a sympathetic nerve marker, and calcitonin gene-related peptide (CGRP)-ir, a sensory nerve marker, were significantly decreased, and BrdU+AD-3-ir adipocytes were increased ∼300%. When IWAT was selectively sensory denervated via local microinjections of capsaicin, a sensory nerve-specific toxin, CGRP-ir, but not TH-ir, was decreased, and BrdU+AD-3-ir adipocytes were unchanged. When IWAT was selectively sympathetically denervated via local microinjections of 6-hydroxy-dopamine, a catecholaminergic-specific toxin, TH-ir, but not CGRP-ir, was significantly decreased, and BrdU+AD-3-ir adipocytes were increased ∼400%. Collectively, these data provide the first direct evidence that sympathetic nerves inhibit white adipocyte proliferation in vivo.
ERK promotes hydrogen peroxide-induced apoptosis through caspase-3 activation and inhibition of Akt in renal epithelial cells
Authors: Zhuang Shougang , Yan Yan , Daubert Rebecca A. , Han Jiahuai , Schnellmann Rick G.
Published: August 2006

Reactive oxygen species, including hydrogen peroxide (H2O2), are generated during ischemia-reperfusion and are critically involved in acute renal failure. The present studies examined the role of the extracellular signal-regulated kinase (ERK) pathway in H2O2-induced renal proximal tubular cells (RPTC) apoptosis. Exposure of RPTC to 1 mM H2O2resulted in apoptosis and activation of ERK1/2 and Akt. Pretreatment with the specific MEK inhibitors, U0126 and PD98059, or adenoviral infection with a construct that encodes a negative mutant of MEK1, protected cells against H2O2-induced apoptosis. In contrast, expression of constitutively active MEK1 enhanced H2O2-induced apoptosis. H2O2induced activation of caspase-3 and phosphorylation of histone H2B at serine 14, a posttranslational modification required for nuclear condensation, which also were blocked by ERK1/2 inhibition. Furthermore, blockade of ERK1/2 resulted in an increase in Akt phosphorylation and blockade of Akt potentiated apoptosis and diminished the protective effect conferred by ERK inhibition in H2O2-treated cells. Although Z-DEVD-FMK, a caspase-3 inhibitor, was able to inhibit histone H2B phosphorylation and apoptosis, it did not affect ERK1/2 phosphorylation. We suggest that ERK elicits apoptosis in epithelial cells by activating caspase-3 and inhibiting Akt pathways and elicits nuclear condensation through caspase-3 and histone H2B phosophorylation during oxidant injury.
Urine concentrating defect in prostaglandin EP1-deficient mice
Authors: Kennedy Chris R. J. , Xiong Huaqi , Rahal Sherine , Vanderluit Jacqueline , Slack Ruth S. , Zhang Yahua , Guan Youfei , Breyer Matthew D. , Hébert Richard L.
Published: August 2006

We investigated the role of the prostaglandin E2(PGE2) EP1receptor in modulating urine concentration as it is expressed along the renal collecting duct where arginine-vasopressin (AVP) exerts its anti-diuretic activity, and in the paraventricular and supraoptic nuclei of the hypothalamus where AVP is synthesized. The urine osmolality of EP1-null mice (EP1−/−) failed to match levels achieved by wild-type (WT) counterparts upon water deprivation (WD) for 24 h. This difference was reflected by higher plasma osmolality in WD EP1−/−mice. Along the collecting duct, the induction and subapical to plasma membrane translocation of the aquaporin-2 water channel in WD EP1−/−mice appeared equivalent to that of WD WT mice as determined by quantitative RT-PCR and immunohistochemistry. However, medullary interstitial osmolalities dropped significantly in EP1−/−mice following WD. Furthermore, urinary AVP levels of WD EP1−/−mice were significantly lower than those of WD WT mice. This deficit could be traced back to a blunted induction of hypothalamic AVP mRNA expression in WD EP1−/−mice as determined by quantitative RT-PCR. Administration of the AVP mimetic [deamino-Cys1,d-Arg8]-vasopressin restored a significant proportion of the urine concentrating ability of WD EP1−/−mice. When mice were water loaded to suppress endogenous AVP production, urine osmolalities increased equally for WT and EP1−/−mice. These data suggest that PGE2modulates urine concentration by acting at EP1receptors, not in the collecting duct, but within the hypothalamus to promote AVP synthesis in response to acute WD.
Erythropoietin and the cardiorenal syndrome: cellular mechanisms on the cardiorenal connectors
Authors: Jie Kim E. , Verhaar Marianne C. , Cramer Maarten-Jan M. , van der Putten Karien , Gaillard Carlo A. J. M. , Doevendans Pieter A. , Koomans Hein A. , Joles Jaap A. , Braam Branko
Published: August 2006

We have recently proposed severe cardiorenal syndrome (SCRS), in which cardiac and renal failure mutually amplify progressive failure of both organs. This frequent pathophysiological condition has an extremely poor prognosis. Interactions between inflammation, the renin-angiotensin system, the balance between the nitric oxide and reactive oxygen species and the sympathetic nervous system form the cardiorenal connectors and are cornerstones in the pathophysiology of SCRS. An absolute deficit of erythropoietin (Epo) and decreased sensitivity to Epo in this syndrome both contribute to the development of anemia, which is more pronounced than renal anemia in the absence of heart failure. Besides expression on erythroid progenitor cells, Epo receptors are present in the heart, kidney, and vascular system, in which activation results in antiapoptosis, proliferation, and possibly antioxidation and anti-inflammation. Interestingly, Epo can improve cardiac and renal function. We have therefore reviewed the literature with respect to Epo and the cardiorenal connectors. Indeed, there are indications that Epo can diminish inflammation, reduce renin-angiotensin system activity, and shift the nitric oxide and reactive oxygen species balance toward nitric oxide. Information about Epo and the sympathetic nervous system is scarce. This analysis underscores the relevance of a further understanding of clinical and cellular mechanisms underlying protective effects of Epo, because this will support better treatment of SCRS.
Characterization of cell clones isolated from hypoxia-selected renal proximal tubular cells
Authors: Brooks Craig , Wang Jinzhao , Yang Tianxin , Dong Zheng
Published: August 2006

Under hypoxia, some cells survive and others are irreversibly injured and die. The factors that determine cell fate under stress remain largely unknown. We recently selected death-resistant cells via repeated episodes of hypoxia. In the present study, 80 clones were isolated from the selected cells and their response to apoptotic injury was characterized. Compared with the wild-type cells, the isolated clones showed a general resistance to apoptosis: 13 were extremely resistant to azide-induced apoptosis, 10 to staurosporine, and 9 to cisplatin. The cell clones that most consistently demonstrated resistance or sensitivity to injury were further studied for their response to azide treatment. Azide induced comparable ATP depletion in these clones and wild-type cells. Hypoxia inducible factor-1 (HIF-1) was upregulated in several clones, but the upregulation did not correlate with cell death resistance. The selected clones maintained an epithelial phenotype, showing typical epithelial morphology, forming “domes” at high density, and expressing E-cadherin. Azide-induced Bax translocation and cytochrome c release, two critical mitochondrial events of apoptosis, were abrogated in death-resistant clones. In addition, cell lysates isolated from these clones showed lower caspase activation on addition of exogenous cytochrome c. Bax, Bak, and Bid expression in these clones was similar to that in wild-type cells, whereas Bcl-2 expression was higher in all the selected clones and, interestingly, Bcl-xL was markedly upregulated in the most death-resistant clones. The results suggest that apoptotic resistance of the selected clones is not determined by a single factor or molecule but, rather, by various alterations at the core apoptotic pathway.
Ventral Pallidum Firing Codes Hedonic Reward: When a Bad Taste Turns Good
Authors: Tindell Amy J. , Smith Kyle S. , Peciña Susana , Berridge Kent C. , Aldridge J. Wayne
Published: August 2006

The ventral pallidum (VP) is a key structure in brain mesocorticolimbic reward circuits that mediate “liking” reactions to sensory pleasures. Do firing patterns in VP actually code sensory pleasure? Strong evidence for hedonic coding requires showing that neural signals track positive increases in sensory pleasure or even reversals from bad to good. A useful test is the salt alliesthesia of physiological sodium depletion that makes even aversively intense NaCl taste become palatable and “liked.” We compared VP neural firing activity in rats during aversive “disliking” reactions elicited by a noxiously intense NaCl taste (triple-seawater 1.5 M concentration) in normal homeostatic state versus in a physiological salt appetite state that made the same NaCl taste palatable and elicit positive “liking” reactions. We also compared firing elicited by palatable sucrose taste, which always elicited “liking” reactions in both states. A dramatic doubling in the amplitude of VP neural firing peaks to NaCl was caused by salt appetite that matched the affective switch from aversive (“disliking”) to positive hedonic (“liking”) reactions. By contrast, VP neural activity to “liked” sucrose taste was always high and never altered. In summary, VP firing activity selectively tracks the hedonic values of tastes, even across hedonic reversals caused by physiological changes. Our data provide the strongest evidence yet for neural hedonic coding of natural sensory pleasures and suggest, by extension, how abnormalities in VP firing patterns might contribute to clinical hedonic dysfunctions.
Distributed and Selective Auditory Representation of Song Repertoires in the Avian Song System
Authors: Nealen Paul M. , Schmidt Marc F.
Published: August 2006

For many songbirds, the vocal repertoire constitutes acoustically distinct songs that are flexibly used in various behavioral contexts. To investigate how these different vocalizations are represented in the song neural system, we presented multiple song stimuli while performing extracellular recording in nucleus HVC in adult male song sparrows Melospiza melodia, a species known for its complex vocal repertoire and territorial use of song. We observed robust auditory responses to natural song stimuli in both awake and anesthetized animals. Auditory responses were selective for multiple songs of the bird's own repertoire (BOR) over acoustically modified versions of these stimuli. Selectivity was evident in both awake and anesthetized HVC, in contrast to auditory selectivity in zebra finch HVC, which is apparent only under anesthesia. Presentation of multiple song stimuli at different recording locations demonstrated that stimulus acoustic features and local neuronal tuning both contribute to auditory responsiveness. HVC auditory responsiveness was broadly distributed and nontopographic. Variance in auditory responsiveness was greater among than within HVC recording locations in both anesthetized and awake birds, in contrast to the global nature of auditory representation within zebra finch HVC. To assess the spatial consistency of auditory representation within HVC, we measured the repeatability with which ensembles of BOR songs were represented across the nucleus. Auditory response ranks to different songs were more consistent across recording locations in awake than in anesthetized animals. This spatial reliability of auditory responsiveness suggests that sound stimulus acoustic features contribute relatively more to auditory responsiveness in awake than in anesthetized animals.
Relationships Between Calcium and pH in the Regulation of the Slow Afterhyperpolarization in Cultured Rat Hippocampal Neurons
Authors: Kelly Tony , Church John
Published: August 2006

The Ca2+-dependent slow afterhyperpolarization (AHP) is an important determinant of neuronal excitability. Although it is established that modest changes in extracellular pH (pHo) modulate the slow AHP, the relative contributions of changes in the priming Ca2+ signal and intracellular pH (pHi) to this effect remain poorly defined. To gain a better understanding of the modulation of the slow AHP by changes in pHo, we performed simultaneous recordings of intracellular free calcium concentration ([Ca2+]i), pHi, and the slow AHP in cultured rat hippocampal neurons coloaded with the Ca2+- and pH-sensitive fluorophores fura-2 and SNARF-5F, respectively, and whole cell patch-clamped using the perforated patch technique. Decreasing pHo from 7.2 to 6.5 lowered pHi, reduced the magnitude of depolarization-evoked [Ca2+]i transients, and inhibited the subsequent slow AHP; opposite effects were observed when pHo was increased from 7.2 to 7.5. Although decreases and increases in pHi (at a constant pHo) reduced and augmented, respectively, the slow AHP in the absence of marked changes in preceding [Ca2+]i transients, the inhibition of the slow AHP by decreases in pHo was correlated with low pHo-dependent reductions in [Ca2+]i transients rather than the decreases in pHi that accompanied the decreases in pHo. In contrast, high pHo-induced increases in the slow AHP were correlated with the accompanying increases in pHi rather than high pHo-dependent increases in [Ca2+]i transients. The results indicate that changes in pHo modulate the slow AHP in a manner that depends on the direction of the pHo change and substantiate a role for changes in pHi in modulating the slow AHP during changes in pHo.
Does Rubella Immunity Predict Measles Immunity? A Serosurvey of Pregnant Women
Authors: Kennedy Colleen M. , Burns Barbara A. , Ault Kevin A.
Published: August 2006

Background. This study was undertaken to determine
whether rubella immunity infers measles immunity in pregnant
women. Methods. Stored serum samples were obtained from
the Iowa State Hygienic Laboratory for evaluation of rubella and
measles immunities with IgG enzyme‐linked immunosorbent
assay. Results. Nine hundred serum samples were obtained for
testing. The average age of the women at the time of antepartum
serum collection was 28 (range, 14 to 44) years. Measles and
rubella immunity were 88% and 98%, respectively; there was no effect of immunity status by age identified. Eighty eight
percent of those with rubella immunity were also measles immune.
There was no association between paired rubella and measles
immunity identified, P < .0001. Discussion. Known rubella immunity did not infer measles immunity in our population. Thus, we recommend that pregnant women exposed to measles be tested and
appropriately treated if they are found to be nonimmune.
Septic Pelvic Thrombophlebitis: Diagnosis and Management
Authors: Garcia Javier , Aboujaoude Ramzi , Apuzzio Joseph , Alvarez Jesus R.
Published: August 2006

Septic pelvic thrombophlebitis (SPT) was initially diagnosed and
described in the late 1800′s. The entity had a high incidence and
mortality during this period of time, and a surgical therapeutic
approach was the treatment of choice. Since then, the diagnosis,
incidence, and management of the entity evolved. This evolution
followed the development of newer diagnostic tools such as
computed tomography (CT), magnetic resonance imaging (MRI), and a
better understanding of the pathophysiology of the disease. The
treatment of SPT has had significant changes as well, from a
surgical approach at the end of the 19th century to a
medical approach after the 1960′s. By using an adequate
broad‐spectrum antibiotic therapy, mortality has decreased.
However, controversy in the management of this entity remains
even till today.
Adherence and Blocking of Candida Albicans to Cultured Vaginal Epithelial Cells: Treatments to Decrease Adherence
Authors: Hollmer Cara , Essmann Michael , Ault Kevin , Larsen Bryan
Published: August 2006

Background. Pathogenesis of mucosal microorganisms
depends on adherence to the tissues they colonize and infect. For
Candida albicans, cell surface hydrophobicity may play a
significant role in tissue binding ability. Methods. A
continuous cell line of vaginal epithelial cells (VEC)
was grown in keratinocyte serum‐free medium (KSFM) with
supplements and harvested by trypsinization. VEC were combined
with yeast cells to evaluate adherence and inhibition of
adherence. In this experimental setup, yeast stained with
fluorescein isothiocyanate were allowed to attach to VEC and the
resulting fluorescent VEC were detected by flow cytometry.
Results. VEC were cultured and examined daily after
plating and showed morphology similar to basal epithelial cells.
Culture media supplemented with estradiol showed increased VEC
proliferation initially (first 24 h) but cell morphology was not
altered. Fluorescinated Candida cells bound effectively
to the cultured VEC. Using fresh cells exposed to various
preparations of K‐Y, we showed that all formulations of the
product reduced Candida binding to VEC by 25% to
50%. While VEC were generally harvested for use in
experiments when they were near confluent growth, we allowed some
cultures to grow beyond that point and discovered that cells
allowed to become overgrown or stressed appeared to bind yeast
cells more effectively. Conclusion. Flow cytometry is a
useful method for evaluating binding of stained yeast cells to
cultured VEC and has demonstrated that commercially available
products have the ability to interfere with the process of yeast
adherence to epithelial cells.