bluuebunny/crossref_metadata_2025 huggingface dataset:
IS GRAVITINO CONDENSATION POSSIBLE?
Authors: POLLOCK M. D.
Published: June 2004

The condensation of fermion bilinears in the dimensionally-reduced, E 8× E '8 heterotic superstring theory often refers to the E'8 hidden-sector gauginos, but in principle condensation may also occur in the compactified internal space, for example of the gravitino and the spin-1/2 Majorana–Weyl field λ of eleven-dimensional supergravity. This possibility, raised by Duff and Orzalesi as a method of spontaneous compactification that maintains vanishing vacuum energy (cosmological constant), was subsequently considered in the context of the heterotic superstring theory by Helayël–Neto and Smith and by the present author, assuming the internal-space gravitinos [Formula: see text] to condense close to the compactification scale M c ~M P /10. Here, by including the four-fermion terms in the Lagrangian density ℒ, we point out that the observable-sector gravitinos ψi and gauginos g typically have comparable, but not identical, masses m3/2~mg~M c as a result of this process. Hence, such condensation is only permitted either at the much lower scale [Formula: see text] (as for the hidden-sector gaugino condensation), so that [Formula: see text], the upper limit on mg ensuring that the Higgs doublets are sufficiently light or, more plausibly, by setting 1 TeV ~mg≪m3/2~M c , which requires a constraint on the condensate parameters. If the three-index field [Formula: see text] also condenses, then the vacuum expectation value of the dimensionless combination [Formula: see text] of the dilaton A r and modulus B r is fixed at a scale ~1, thus yielding the Kähler potential K and hence m3/2~M c Since B r is determined from supersymmetry, this mechanism determines A r .
BLACK HOLE QUANTIZATION, THERMODYNAMICS AND COSMOLOGICAL CONSTANT
Authors: XIANG LI
Published: June 2004

Bekenstein argues that the horizon area of a black hole has a constant distance spectrum. We investigate the effects of such a discrete spectrum on the thermodynamics of a Schwarzchild black hole (SBH) and a Schwarzchild–de Sitter black hole (SdBH), in terms of the time-energy uncertainty relation and Stefan–Boltzman law. For the massive SBH, a negative and logarithmic correction to the Bekenstein–Hawking entropy is obtained, as well as other authors by using other methods. As to the minimal hole near the Planck scale, its entropy is no longer proportional to the horizon area, but is of order of the mass of the hole. This is similar to an excited stringy state. The vanishing heat capacity of such a minimal black hole implies that it may be a remnant as the ground state of the evaporating hole. The properties of a SdBH are similar to the SBH, except for an additional term of square area associated with the cosmological constant. In order to maintain the validity of the Bekenstein–Hawking formula, the cosmological constant is strongly limited by the size of the biggest black hole in the universe. A relation associated with the cosmological constant, Planck area and the Stefan–Boltzman constant is obtained. The cosmological constant is not only related to the vacuum energy, but is also related to the thermodynamics.
A CAUSAL MODEL FOR A CLOSED UNIVERSE
Authors: CATALDO MAURICIO , DEL CAMPO SERGIO , MINNING PAUL , PEÑA FRANCISCO
Published: June 2004

We study a closed model of a universe filled with viscous fluid and quintessence matter components. The dynamical equations imply that the universe might look like an accelerated flat Friedmann–Robertson–Walker (FRW) universe at low redshift. We consider here dissipative processes which obey a causal thermodynamics. Here, we account for the entropy production via causal dissipative inflation.
MEASURING THE INTERPLANETARY MEDIUM WITH A SOLAR SAIL
Authors: NIETO MICHAEL MARTIN , TURYSHEV SLAVA G.
Published: June 2004

NASA has been considering a solar sail that would accelerate a craft to a high velocity (~14 AU/yr) by the time it reached 5 AU. Then the sail would be dropped and the craft would coast alone to deep space. We propose that the sail be retained longer. Then the density of the interplanetary medium could be determined by measuring the drag force on the huge sail using radiometric navigational data. Such an experiment would yield an independent, new type of measurement of the interplanetary medium and should be pursued.
PROPERTIES OF FOUR NUMERICAL SCHEMES APPLIED TO A NONLINEAR SCALAR WAVE EQUATION WITH A GR-TYPE NONLINEARITY
Authors: HANSEN JAKOB , KHOKHLOV ALEXEI , NOVIKOV IGOR
Published: June 2004

We study stability, dispersion and dissipation properties of four numerical schemes (Itera-tive Crank–Nicolson, 3rd and 4th order Runge–Kutta and Courant–Fredrichs–Levy Nonlinear). By use of a Von Neumann analysis we study the schemes applied to a scalar linear wave equation as well as a scalar nonlinear wave equation with a type of nonlinearity present in GR-equations. Numerical testing is done to verify analytic results. We find that the method of lines (MOL) schemes are the most dispersive and dissipative schemes. The Courant–Fredrichs–Levy Nonlinear (CFLN) scheme is most accurate and least dispersive and dissipative, but the absence of dissipation at Nyquist frequency, if fact, puts it at a disadvantage in numerical simulation. Overall, the 4th order Runge–Kutta scheme, which has the least amount of dissipation among the MOL schemes, seems to be the most suitable compromise between the overall accuracy and damping at short wavelengths.
RISK SENSITIVITIES OF BERMUDA SWAPTIONS
Authors: PITERBARG VLADIMIR V.
Published: June 2004

A new approach to the problem of computing risk sensitivities of Bermuda swaptions in a lattice, or PDE, framework is presented. The algorithms developed perform the task much faster and more accurately that the traditional approach in which the Greeks are computed numerically by shocking the appropriate inputs and revaluing the instrument. The time needed to execute the tradition scheme grows linearly with the number of Greeks required, whereas our approach computes any number of Greeks for a Bermuda swaption in nearly constant time. The new method explores symmetries in the structure of Bermuda swaptions to derive recursive relations between different Greeks, and is essentially model-independent. These recursive relations allow us to represent risk sensitivities in a number of ways, in particular as integrals over the "survival" density. The survival density is obtained as a solution to a forward Kolmogorov equation. This representation is the basis for practical applications of our approach.
STORAGE OPTIONS VALUATION USING MULTILEVEL TREES AND CALENDAR SPREADS
Authors: MANOLIU MIHAELA
Published: June 2004

We present a detailed description of storage options valuation using a multilevel tree methodology which takes into account both the stochastic evolution of the energy commodity price underlying the storage contract or asset, as well as the storage facility operational constraints. We derive also a quasi-analytical solution for the storage value as a strip of calendar spread options, which is applicable when the storage constraints are ignored. The two valuation methodologies are applied within the framework of a one-factor and a two-factor diffusion model for the commodity price. As an interesting example of a path-dependent option with American exercise style, we take a look at the storage option injection and withdrawal exercise price boundaries and examine how these exercise decision boundaries are influenced by variations in the model's input parameters. We provide numerical results illustrating the dependence of the storage option value on the price model parameters, and interpret the observed parameter dependence using the calendar spreads formula as a useful analysis tool. We analyze and present numerical results regarding the dependence of the option value on the storage operational parameters.
INTEGRATION OF GLOBAL CAPITAL MARKETS: AN EMPIRICAL EXPLORATION
Authors: BHATTACHARYYA MALAY , BANERJEE ASHOK
Published: June 2004

It is generally argued that with lifting of barriers to the flow of capital across countries by respective governments, the capital markets have come closer and are now more integrated. This paper examines the existence (or absence) of integration among stock indices of 11 developed and emerging stock markets from three continents: Asia, Europe and America. Using synchronous weekly closing index values from November, 1990 through December, 2001, the study found that all the 11 stock markets are cointegrated. The cointegration analysis was carried out using an error correction vector autoregression (VECM) model. The study goes further to test whether there are any causal relationships among the indices and has used a hitherto empirically untested methodology to explore the causal relationships. Results show that capital market indices from European countries and the USA are not Granger caused by any index. On the other hand, causality effects are much pronounced in Asian capital markets. The capital market in Hong Kong "leads" the other markets in Asia. This learning would help fund managers in managing their exposure in Asian capital markets. The regulators may use the causality results to identify the markets driving movements in a country's capital market and take corrective measures.
A Fundamental Framework for Knowledge Management Implementation in SMEs
Authors: Wong Kuan Yew , Aspinwall Elaine
Published: June 2004

Knowledge management (KM) is a business discipline that is currently dominated by large businesses. SMEs are generally trailing behind them in terms of applying KM principles. Various frameworks have been developed and reported in the literature, but they possess drawbacks. The characteristics, features and needs of SMEs are often not reflected in them. This paper introduces a framework for implementing KM in the SME sector, which is centred on six major themes: the types of knowledge to be managed, the socio-technical perspective of KM, the formation of a KM coordinating group, the initiatives to be implemented, a guide to deploying these initiatives, and the tools and techniques to support them. A pilot study involving a small group of academics and practitioners in the KM field was used to make a preliminary assessment of it prior to testing it in SMEs. Overall, their evaluation indicated a positive view towards the framework.
Facilitating Idea Generation and Decision-Making with Concept Maps
Authors: Coffey John W.
Published: June 2004

This paper contains a description of the creation of Concept Maps in facilitated sessions to promote idea generation and group decision-making. A number of issues pertain to facilitated Concept Mapping, including the number of facilitators, the optimal or manageable size of groups, the sorts of group interactions that are encountered and their impacts on the proceedings, and the sorts of outcomes that can be expected. This article describes these basic issues as well as attributes, concerns, and skills required of facilitators. It presents two case studies illustrating methodological issues pertaining to the facilitation process and the sorts of outcomes that can be achieved.
VARIATIONAL PRINCIPLES FOR INVOLUTIVE SYSTEMS OF VECTOR FIELDS
Authors: GAETA GIUSEPPE , MORANDO PAOLA
Published: June 2004

In many relevant cases — e.g., in Hamiltonian dynamics — a given vector field can be characterized by means of a variational principle based on a one-form. We discuss how a vector field on a manifold can also be characterized in a similar way by means of a higher-order variational principle, and how this extends to involutive systems of vector fields.
Immunolocalization of type 2 inositol 1,4,5-trisphosphate receptors in cardiac myocytes from newborn mice
Authors: García Kelly D. , Shah Tanvi , García Jesús
Published: June 2004

The precise localization and role of inositol 1,4,5-trisphosphate (InsP3) receptors (InsP3Rs) in cardiac muscle cells are largely unknown. It is believed that waves and oscillations in cytosolic free calcium triggered by activation of InsP3Rs underlie modifications of cellular responses that lead to changes in gene expression in other cells. However, how changes in cytosolic calcium alter gene expression in cardiac cells is unknown. Moreover, it is unclear how changes in cytosolic calcium that alter gene expression do so independently of effects of calcium on other cellular functions, such as contraction. Here we show that InsP3R type 2 is the only isoform present in cardiac myocytes isolated from neonatal mouse ventricles. We also show that type 2 InsP3Rs are associated with the nucleus and that activation of type 2 InsP3Rs with endothelin-1 or phenylephrine selectively increases transcription of atrial natriuretic factor and skeletal α-actin. Type 2 InsP3Rs are also in striations. Activation of InsP3Rs with adenophostin A in permeabilized cells induced calcium release in the nuclear domain and other regions of the cell away from the nucleus. Agonist-induced increase in gene expression and calcium release were blocked by the InsP3R inhibitors 2-aminoethoxydiphenyl borate and xestospongin C. The spatial separation of type 2 InsP3Rs provides support for the concept that microdomains of calcium discretely alter various cell processes. Our experiments suggest that calcium released by InsP3Rs in the nuclear domain provides a direct mechanism for the control of gene expression, whereas release of calcium in the cytoplasm may modulate other processes, such as contraction.
Role of TGF-β1 and JNK signaling in capillary tube patterning
Authors: Bein Kiflai , Odell-Fiddler Elizabeth T. , Drinane Mary
Published: June 2004

The transforming growth factor (TGF) family of secretory polypeptides comprises signaling proteins involved in numerous physiological processes, including vascular development and vessel wall integrity. Both pro- and anti-angiogenic effects of TGF-β1 have also been documented. To study the intracellular mechanisms involved in capillary tube morphogenesis, endothelial cell aggregates were cultured in a fibrin matrix. It was found that the pattern of capillary tubes formed in a fibrin matrix was altered in response to TGF-β1 treatment such that the capillary-like structures displayed a bipolarized pattern. In contrast, in untreated control and fibroblast growth factor-2-treated cells, the pattern of capillary tubes formed was random. TGF-β1 also downregulated urokinase-type plasminogen activator (uPA) activity while upregulating PA inhibitor (PAI)-1 and thrombospondin (TSP)1 gene expression. To investigate the signaling cascade mediating the phenotypic changes observed, pharmacological inhibitors of p38 MAPK, Sp1 transcription factor, c-Jun NH2-terminal kinase (JNK), and the cytokine TNF-α were used. The p38 MAPK inhibitor SB203580 reversed the TGF-β1-dependent inhibition of uPA activity but not its morphogenetic effect. In contrast, the DNA intercalator WP631 and TNF-α counteracted the TGF-β1-induced morphogenetic effect while the JNK inhibitor SP600125 effectively inhibited capillary tube formation. These results indicate that the TGF-β1-induced capillary tube pattern is independent of the p38 MAPK-activated PAI-1 and TSP1 expression, but the mechanism involves Sp1-dependent transcriptional regulation. The results also raise the possibility that the JNK pathway, which controls convergent extension in Xenopus, may be involved in vessel wall patterning in mammalian systems.
Functional analysis of the R1086H malignant hyperthermia mutation in the DHPR reveals an unexpected influence of the III-IV loop on skeletal muscle EC coupling
Authors: Weiss Regina G. , O’Connell Kristen M. S. , Flucher Bernhard E. , Allen Paul D. , Grabner Manfred , Dirksen Robert T.
Published: June 2004

Malignant hyperthermia (MH) is an inherited pharmacogenetic disorder caused by mutations in the skeletal muscle ryanodine receptor (RyR1) and the dihydropyridine receptor (DHPR) α1S-subunit. We characterized the effects of an MH mutation in the DHPR cytoplasmic III-IV loop of α1S (R1086H) on DHPR-RyR1 coupling after reconstitution in dysgenic (α1S null) myotubes. Compared with wild-type α1S, caffeine-activated Ca2+ release occurred at approximately fivefold lower concentrations in nonexpressing and R1086H-expressing myotubes. Although maximal voltage-gated Ca2+ release was similar in α1S- and R1086H-expressing myotubes, the voltage dependence of Ca2+ release was shifted ∼5 mV to more negative potentials in R1086H-expressing myotubes. Our results demonstrate that α1S functions as a negative allosteric modulator of release channel activation by caffeine/voltage and that the R1086H MH mutation in the intracellular III-IV linker disrupts this negative regulatory influence. Moreover, a low caffeine concentration (2 mM) caused a similar shift in voltage dependence of Ca2+ release in α1S- and R1086H-expressing myotubes. Compared with α1S-expressing myotubes, maximal L channel conductance ( Gmax) was reduced in R1086H-expressing myotubes (α1S 130 ± 10.2, R1086H 88 ± 6.8 nS/nF; P < 0.05). The decrease in Gmax did not result from a change in retrograde coupling with RyR1 as maximal conductance-charge movement ratio ( Gmax/Qmax) was similar in α1S- and R1086H-expressing myotubes and a similar decrease in Gmax was observed for an analogous mutation engineered into the cardiac L channel (R1217H). In addition, both R1086H and R1217H DHPRs targeted normally and colocalized with RyR1 in sarcoplasmic reticulum (SR)-sarcolemmal junctions. These results indicate that the R1086H MH mutation in α1S enhances RyR1 sensitivity to activation by both endogenous (voltage sensor) and exogenous (caffeine) activators.
Different modes of sodium-d-glucose cotransporter-mediated d-glucose uptake regulation in Caco-2 cells
Authors: Khoursandi Saeed , Scharlau Daniel , Herter Peter , Kuhnen Cornelius , Martin Dirk , Kinne Rolf K. H. , Kipp Helmut
Published: June 2004

We recently reported that a considerable amount of the sodium-d-glucose cotransporter SGLT1 present in Caco-2 cells, a model for human enterocytes, is located in intracellular compartments attached to microtubules (Kipp H, Khoursandi S, Scharlau D, and Kinne RKH. Am J Physiol Cell Physiol 285: C737–C749, 2003). A similar distribution pattern was also observed in enterocytes in thin sections from human jejunum, highlighting the validity of the Caco-2 cell model. Fluorescent surface labeling of live Caco-2 cells revealed that the intracellular compartments containing SGLT1 were accessible by endocytosis. To elucidate the role of endosomal SGLT1 in the regulation of sodium-dependent d-glucose uptake into enterocytes, we compared SGLT1-mediated d-glucose uptake into Caco-2 cells with the subcellular distribution of SGLT1 after challenging the cells with different stimuli. Incubation (90 min) of Caco-2 cells with mastoparan (50 μM), a drug that enhances apical endocytosis, shifted a large amount of SGLT1 from the apical membrane to intracellular sites and significantly reduced sodium-dependent α-[14C]methyl-d-glucose uptake (−60%). We also investigated the effect of altered extracellular d-glucose levels. Cells preincubated (1 h) with d-glucose-free medium exhibited significantly higher sodium-dependent α-[14C]methyl-d-glucose uptake (+45%) than did cells preincubated with high d-glucose medium (100 mM, 1 h). Interestingly, regulation of SGLT1-mediated d-glucose uptake into Caco-2 cells by extracellular d-glucose levels occurred without redistribution of cellular SGLT1. These data suggest that, pharmacologically, d-glucose uptake can be regulated by a shift of SGLT1 between the plasma membrane and the endosomal pool; however, regulation by the physiological substrate d-glucose can be explained only by an alternative mechanism.
Role of immunoreceptor tyrosine-based inhibitory motifs of PECAM-1 in PECAM-1-dependent cell migration
Authors: O’Brien Christopher D. , Cao Gaoyuan , Makrigiannakis Antonis , DeLisser Horace M.
Published: June 2004

Platelet endothelial cell adhesion molecule (PECAM-1), a transmembrane glycoprotein, has been implicated in angiogenesis, with recent evidence indicating the involvement of PECAM-1 in endothelial cell motility. The cytoplasmic domain of PECAM-1 contains two tyrosine residues, Y663 and Y686, that each fall within an immunoreceptor tyrosine-based inhibitory motif (ITIM). When phosphorylated, these residues together mediate the binding of the protein tyrosine phosphatase SHP-2. Because SHP-2 has been shown to be involved in the turnover of focal adhesions, a phenomenon required for efficient cell motility, the association of this phosphatase with PECAM-1 via its ITIMs may represent a mechanism by which PECAM-1 might facilitate cell migration. Studies were therefore done with cell transfectants expressing wild-type PECAM or mutant PECAM-1 in which residues Y663 and Y686 were mutated. These mutations eliminated PECAM-1 tyrosine phosphorylation and the association of PECAM-1 with SHP-2 but did not impair the ability of the molecule to localize at intercellular junctions or to bind homophilically. However, in vitro cell motility and tube formation stimulated by the expression of wild-type PECAM-1 were abrogated by the mutation of these tyrosine residues. Importantly, during wound-induced migration, the number of focal adhesions as well as the level of tyrosine phosphorylated paxillin detected in cells expressing wild-type PECAM-1 were markedly reduced compared with control cells or transfectants with mutant PECAM-1. These data suggest that, in vivo, the binding of SHP-2 to PECAM-1, via PECAM-1’s ITIM domains, promotes the turnover of focal adhesions and, hence, endothelial cell motility.
Suppression of DHEA sulfotransferase (Sult2A1) during the acute-phase response
Authors: Kim Min Sun , Shigenaga Judy , Moser Art , Grunfeld Carl , Feingold Kenneth R.
Published: June 2004

The acute-phase response (APR) induces alterations in lipid metabolism, and our data suggest that this is associated with suppression of type II nuclear hormone receptors that are key regulators of fatty acid, cholesterol, and bile acid metabolism. Recently, the farnesoid X receptor (FXR), constitutive androstane receptor (CAR), and pregnane X receptor (PXR) were found to regulate DHEA sulfotransferase (Sult2A1), which plays an important role in DHEA sulfation and detoxification of bile acids. Because FXR, PXR, and CAR are suppressed during the APR, we hypothesized that Sult2A1 is downregulated during the APR. To induce the APR, mice were treated with LPS, which will then trigger the release of various cytokines, and the mRNA levels of Sult2A1 and the sulfate donor 3′-phosphoadenosine 5′-phosphosulfate synthase 2 (PAPSS2), as well as the enzyme activity of Sult2A1, were determined in the liver. We found that mRNA levels of Sult2A1 decrease in a time- and dose-dependent manner during the LPS-induced APR. Similar changes were observed in the mRNA levels of PAPSS2, the major synthase of PAPS in the liver. Moreover, hepatic Sult2A1 activity and serum levels of DHEA-sulfate (DHEA-S) were significantly decreased in LPS-treated animals. These results suggest that decreased levels or activities of FXR, PXR, and CAR during the APR could contribute to decreases in Sult2A1, resulting in decreased sulfation of DHEA and lower circulating level of DHEA-S. Finally, we found that both TNF and IL-1 caused a significant decrease in the mRNA level of Sult2A1 in Hep3B human hepatoma cells, suggesting that the proinflammatory cytokines TNF and IL-1 mediate the inhibitory effect of LPS on Sult2A1 mRNA level. Our study provides a possible mechanism by which infection and inflammation are associated with altered steroid metabolism and cholestasis.
Two TTX-resistant Na+ currents in mouse colonic dorsal root ganglia neurons and their role in colitis-induced hyperexcitability
Authors: Beyak Michael J. , Ramji Noor , Krol Karmen M. , Kawaja Michael D. , Vanner Stephen J.
Published: June 2004

The composition of Na+ currents in dorsal root ganglia (DRG) neurons depends on their neuronal phenotype and innervation target. Two TTX-resistant (TTX-R) Na+ currents [voltage-gated Na channels (Na v)] have been described in small DRG neurons; one with slow inactivation kinetics (Na v1.8) and the other with persistent kinetics (Na v1.9), and their modulation has been implicated in inflammatory pain. This has not been studied in neurons projecting to the colon. This study examined the relative importance of these currents in inflammation-induced changes in a mouse model of inflammatory bowel disease. Colonic sensory neurons were retrogradely labeled, and colitis was induced by instillation of trinitrobenzenesulfonic acid (TNBS) into the lumen of the distal colon. Seven to ten days later, immunohistochemical properties were characterized in controls, and whole cell recordings were obtained from small (<40 pF) labeled DRG neurons from control and TNBS animals. Most neurons exhibited both fast TTX-sensitive (TTX-S)- and slow TTX-R-inactivating Na+ currents, but persistent TTX-R currents were uncommon (<15%). Most labeled neurons were CGRP (79%), tyrosine kinase A (trkA) (84%) immunoreactive, but only a small minority bind IB4 (14%). TNBS-colitis caused ulceration, thickening of the colon and significantly increased neuronal excitability. The slow TTX-R-inactivating Na current density (Na v1.8) was significantly increased, but other Na currents were unaffected. Most small mouse colonic sensory neurons are CGRP, trkA immunoreactive, but not isolectin B4 reactive and exhibit fast TTX-S, slow TTX-R, but not persistent TTX-R Na+ currents. Colitis-induced hyperexcitability is associated with increased slow TTX-R (Na v1.8) Na+ current. Together, these findings suggest that colitis alters trkA-positive neurons to preferentially increase slow TTX-R Na+ (Na v1.8) currents.
Modulation of neurotransmitter release by NO is altered in mesenteric arterial bed of spontaneously hypertensive rats
Authors: Kolo Lacy L. , Westfall Thomas C. , Macarthur Heather
Published: June 2004

Nitric oxide (NO) reacts with catecholamines resulting in their deactivation. In the present study with the use of the perfused mesenteric arterial bed as a model of the sympathetic neuroeffector junction, the NO synthase (NOS) inhibitor Nω-nitro-l-arginine methyl ester (l-NAME) resulted in the enhancement of the periarterial nerve stimulation-induced increase in perfusion pressure and norepinephrine overflow while decreasing neuropeptide Y (NPY) overflow. These changes were prevented by l-arginine, demonstrating that the effects of l-NAME were specific to the inhibition of NOS. From the fact that norepinephrine acts on prejunctional α2-adrenoceptors to inhibit the evoked release of sympathetic cotransmitters, we carried out experiments in the presence of the α2-adrenergic receptor antagonist yohimbine to investigate the possibility that the decrease in NPY observed in the presence of l-NAME was due to the increase in bioactive norepinephrine acting on its autoreceptor. Periarterial nerve stimulation in the presence of both l-NAME and yohimbine prevented the previously observed decrease in NPY, indicating that the cause of this decrease was, as predicted, due to α2-adrenoceptor activation. The periarterial nerve stimulation-induced increase of norepinephrine overflow was greater in the spontaneously hypertensive rat compared with normotensive rats. In contrast to what was observed in the isolated perfused mesenteric arterial bed obtained from normotensive animals, inhibition of NOS did not result in a further increase in the overflow of norepinephine or in a subsequent decrease in NPY. These results demonstrate that, in addition to being a direct vasodilator, NO, by deactivating norepinephrine, can modulate sympathetic neurotransmission and that this modulation is altered in the spontaneously hypertensive rat.
Pathophysiological plasma ET-1 levels antagonize β-adrenergic dilation of coronary resistance vessels in conscious dogs
Authors: Okajima Masaki , Parent Robert , Thorin Eric , Lavallée Michel
Published: June 2004

On the basis of in vitro experiments showing that endothelin (ET)-1 interferes with smooth muscle ATP-sensitive K+ (KATP) channel opening, which is pivotal in β-adrenergic coronary dilation, we hypothesized that pathophysiological plasma ET-1 levels impair β-adrenergic dilation of resistance coronary vessels. In conscious instrumented dogs, graded intravenous doses of dobutamine caused the expected inotropic responses. As myocardial O2 consumption (MV̇o2) increased, the disproportionate rise in coronary sinus (CS) Po2 indicates that increases in coronary blood flow (CBF) exceeded metabolic requirements, consistent with β-adrenergic dilation. ET-1 intravenous infusions, to reach pathophysiological plasma levels, reduced slopes of the Po2-MV̇o2 and CBF-MV̇o2 relations. In contrast, the first derivative of left ventricular pressure over time responses to dobutamine were not impaired during ET-1 delivery. Clazosentan, an ETA receptor blocker, prevented reduction of the slope of Po2-MV̇o2 and CBF-MV̇o2 relations. After ganglionic blockade to exclude reflex influences, ET-1 still reduced slopes of Po2-MV̇o2 and CBF-MV̇o2 relations. To assess effects of ET-1 on endothelium-dependent and -independent coronary vascular responses, intracoronary ACh and nitroglycerin were given to directly target coronary vessels. CBF responses to ACh and nitroglycerin were maintained during ET-1 delivery. In contrast, responses to intracoronary KATP channel-dependent dilators adenosine and lemakalim were impaired by ET-1. In conclusion, pathophysiological levels of ET-1 impaired β-adrenergic dilation of resistance coronary vessels through an ETA receptor-dependent process. In contrast, left ventricular inotropic responses to dobutamine were not impaired during ET-1 delivery. Our data suggest that ET-1 may interfere with smooth muscle KATP channels to impair β-adrenergic coronary dilation.
Diabetes decreases rabbit bladder smooth muscle contraction while increasing levels of myosin light chain phosphorylation
Authors: Su Xiaoling , Changolkar Arun , Chacko Samuel , Moreland Robert S.
Published: June 2004

The effect of diabetes mellitus on the regulation of urinary bladder smooth muscle contraction was studied. Diabetes was induced in the rabbit by alloxan injection followed by 16 wk of housing. The bladder was harvested and strips of wall devoid of both mucosa and serosa were examined. Intact strips of bladder smooth muscle from diabetic animals produced less stress in response to membrane depolarization than muscle from control animals; sensitivity to KCl was not changed. Carbachol responses were similar in muscle strips from the two animal groups. Basal myosin light chain (MLC) phosphorylation levels were significantly elevated in response to most stimuli in muscle strips from diabetic animals, although levels of stress were either unchanged or lower. α-Toxin-permeabilized strips that allow for control of the intracellular environment while maintaining excitation-contraction coupling showed increased levels of MLC phosphorylation but decreased sensitivity to activator Ca2+in smooth muscle from diabetic animals. MLC phosphatase contents were similar in smooth muscle from the two animal groups; however, MLC phosphatase activity was greater in muscle from control compared with diabetic animals. These results suggest that diabetes mellitus uncouples basal MLC phosphorylation from force in the bladder smooth muscle cell.
Adenosine Inhibits GABAergic and Glycinergic Transmission in Adult Rat Substantia Gelatinosa Neurons
Authors: Yang Kun , Fujita Tsugumi , Kumamoto Eiichi
Published: June 2004

The effect of adenosine on inhibitory postsynaptic currents (IPSCs) was examined in substantia gelatinosa (SG) neurons of adult rat spinal cord slices by using the whole cell patch-clamp technique. Adenosine reversibly reduced the amplitude of GABAergic and glycinergic electrically evoked IPSCs (eIPSCs) in a dose-dependent manner (EC50 = 14.5 and 19.1 μM, respectively). The A1 adenosine-receptor agonist N6-cyclopentyladenosine also reduced the eIPSCs, whereas the A1 antagonist 8-cyclopentyl-1,3-dimethylxanthine reversed the inhibition produced by adenosine. In paired-pulse experiments, the ratio of the second to first GABAergic or glycinergic eIPSC amplitude was increased by adenosine, whereas the response of SG neurons to exogenous GABA or glycine was unaffected. Adenosine reduced the frequency of GABAergic and glycinergic spontaneous IPSCs without changing their amplitude. This reduction in frequency disappeared in the presence of a K+-channel blocker (4-aminopyridine) but not in the absence of Ca2+. The inhibition by adenosine disappeared in the presence of cyclic-AMP analog (8-Br-cyclic AMP) and adenylate-cyclase activator (forskolin) but not protein-kinase C (PKC) activator (phorbol-12,13-dibutyrate). We conclude that adenosine suppresses inhibitory transmission in SG neurons by activating presynaptic A1 receptors and that this action is mediated by K+ channels and cyclic AMP but not by Ca2+ channels and PKC. This inhibitory action of adenosine probably contributes to the modulation of pain transmission in the SG.
Protective Effect of Ifenprodil Against Spreading Depression in the Mouse Entorhinal Cortex
Authors: Faria Leonardo Coutinho , Mody Istvan
Published: June 2004

In the brain, spreading depression (SD) is characterized by a large extracellular DC shift, a massive failure of ion homeostasis and a transient cessation of neuronal function. Clinically, SD is believed to be involved in various neurological disorders including migraine and cerebrovascular diseases. The propagation of cortical SD requires the release of glutamate, and N-methyl-d-aspartate (NMDA) receptors play a crucial role in this process. Here, we have isolated the NMDA receptor-mediated component of extracellularly recorded field excitatory postsynaptic potentials (fEPSPs) in layers 2–3 of the entorhinal cortex of murine brain slices. In the absence of GABAA and AMPA receptor-mediated synaptic transmission, stimulation of layer 6 afferents every 15–90 s elicited spontaneous SD on average within 18.5 min after the start of the stimulation. In the presence of ifenprodil, an NR2B receptor subunit-selective NMDA receptor antagonist, the occurrence of SD was nearly abolished. Our results are consistent with an important role of NR2B subunits in triggering SD in the entorhinal cortex.
Functional Connectivity in Layer IV Local Excitatory Circuits of Rat Somatosensory Cortex
Authors: Cowan Anna I. , Stricker Christian
Published: June 2004

There are two types of excitatory neurons within layer IV of rat somatosensory cortex: star pyramidal (SP) and spiny stellate cells (SS). We examined the intrinsic properties and connectivity between these neurons to determine differences in function. Eighty-four whole cell recordings of pairs of neurons were examined in slices of rat barrel cortex at 36 ± 1°C. Only minimal differences in intrinsic properties were found; however, differences in synaptic strength could clearly be shown. Connections between homonymous pairs (SS–SS or SP–SP) had a higher efficacy than heteronymous connections. This difference was mainly a result of quantal content. In 42 pairs, synaptic dynamics were examined. Sequences of action potentials (3–20 Hz) in the presynaptic neuron consistently caused synaptic depression ( Ē2/ Ē1 = 0.53 ± 0.18). The dominant component of depression was release-independent; this depression occurred even when preceding action potentials had failed to cause a response. The release-dependence of depression was target specific; in addition, release-independence was greater for postsynaptic SPs. In a subset of connections formed only between SP and any other cell type (43%), synaptic efficacy was dependent on the presynaptic membrane potential ( Vm); at −55 mV, the connections were almost silent, whereas at −85 mV, transmission was very reliable. We suggest that, within layer IV, there is stronger efficacy between homonymous than between heteronymous excitatory connections. Under dynamic conditions, the functional connectivity is shaped by synaptic efficacy at individual connections, by Vm, and by the specificity in the types of synaptic depression.
Preventing Cancer, Cardiovascular Disease, and Diabetes
Authors: Eyre Harmon , Kahn Richard , Robertson Rose Marie ,   the ACS/ADA/AHA Collaborative Writing Committee,   ACS/ADA/AHA Collaborative Writing Committee Members, Clark Nathaniel G. , Doyle Colleen , Hong Yuling , Gansler Ted , Glynn Thomas , Smith Robert A. , Taubert Kathryn , Thun Michael J.
Published: June 2004

Collectively, cardiovascular disease (including stroke), cancer, and diabetes account for approximately two thirds of all deaths in the United States and about $700 billion in direct and indirect economic costs each year. Current approaches to health promotion and prevention of cardiovascular disease, cancer, and diabetes do not approach the potential of the existing state of knowledge. A concerted effort to increase application of public health and clinical interventions of known efficacy to reduce prevalence of tobacco use, poor diet, and insufficient physical activity—the major risk factors for these diseases—and to increase utilization of screening tests for their early detection could substantially reduce the human and economic cost of these diseases. In this article, the ACS, ADA, and AHA review strategies for the prevention and early detection of cancer, cardiovascular disease, and diabetes, as the beginning of a new collaboration among the three organizations. The goal of this joint venture is to stimulate substantial improvements in primary prevention and early detection through collaboration between key organizations, greater public awareness about healthy lifestyles, legislative action that results in more funding for and access to primary prevention programs and research, and reconsideration of the concept of the periodic medical checkup as an effective platform for prevention, early detection, and treatment.
Parental Socialization and Community Context: A Longitudinal Analysis of the Structural Sources of Low Self-Control
Authors: Pratt Travis C. , Turner Michael G. , Piquero Alex R.
Published: June 2004

Several empirical studies have attempted to estimate the effect of low self-control on criminal and “analogous” behaviors. Most of these studies have shown that low self-control is an important feature of the cause(s) of crime. Although research is beginning to emerge that targets more specifically the “roots” of self-control via parental socialization (the most salient factor in the development of self-control according to Hirschi and Gottfredson), researchers have yet to explore the degree to which the structural characteristics of communities may influence patterns of parental socialization and, in turn, individual levels of self-control. To address this question, the authors employ longitudinal data from the National Longitudinal Survey of Youth (NLSY) to examine community-level influences on parental socialization and self-control. The results indicate (1) self-control was predicted both cross-sectionally and longitudinally by both parental socialization and adverse neighborhood conditions, (2) the total effect of adverse neighborhood conditions on children’s levels of self-control was just as strong as the total effect for indicators of parental socialization, and (3) important race differences did emerge, particularly with regard to the inter-relationships between our neighborhood-level measures and parental socialization.
A Typology of Street Criminal Retaliation
Authors: Jacobs Bruce A.
Published: June 2004

Criminologists have long recognized that retaliatory violence diffuses outward from discrete conflicts, often in contagion-like fashion. No understanding of the source of this spread is possible without first documenting the modalities that fuel it. Retaliation has variation, and it is important to catalog that variation if the concept of crime as social control is to be more effectively understood. Drawing from in-depth interviews with 33 street offenders, and using qualitative techniques of analytic induction, constant comparison, and domain analysis, this article offers a typology of retaliation to refine understanding of a process that at present, remains only loosely developed.
A Goal-Directed Approach to Gaining Compliance
Authors: Kellermann Kathy
Published: June 2004

This research examines how particular face threats intrinsic to compliance gaining goals constrain compliance gaining behaviors, finding that (a) threats to certain negative and positive face wants differentiate compliance gaining goals from each other; (b) compliance gaining goals are distinct from each other in their arrangements of the number and kind of both appropriate and inappropriate, and efficient and inefficient, compliance gaining behaviors, particularly the goals of stopping an annoying habit, getting a date, asking a favor, and ending a relationship; and (c) a compliance gaining goal’s restriction of cointeractants’ autonomy accounts for differences in which compliance gaining behaviors are judged more and less appropriate, and which more and less efficient, for different compliance gaining goals. Although compliance gaining goals differentially threaten aspects of both negative and positive face, a goal’s autonomy restriction, although not its negative affect potential, relates systematically to the appropriateness and efficiency arrangements of compliance gaining behaviors.
Testing the Cognitive Mediation Model
Authors: Beaudoin Christopher E. , Thorson Esther
Published: June 2004

With data from a 2000 telephone survey of a Midwestern community, the current study tests and reevaluates the cognitive mediation model. In doing so, the authors experiment with a news reliance index and three gratifications sought dimensions: surveillance, anticipated interaction, and guidance. Although there is support for the surveillance and guidance versions of the cognitive mediation model, findings change greatly with the inclusion of anticipated interaction gratifications sought. In a model with the three gratifications sought, the effects of surveillance and guidance on political knowledge fall out, whereas that of anticipated interaction is direct and unmediated. The authors explain these findings with reference to previous research and comment on how different measures of media use and gratifications sought may alter the cognitive mediation model.
Toward a Dual-Process Model of Work-Home Interference
Authors: Bakker Arnold B. , Geurts Sabine A. E.
Published: June 2004

This article introduces the dual-process model of work-home interference (WHI), which claims that job characteristics can be categorized in two broad categories, job demands and job resources, that are differentially related to job-related outcomes and WHI measures. The model proposes that job demands are primarily related to feelings of exhaustion, whereas job resources are primarily related to work-related flow. The central hypothesis of the current study among 1,090 employees was that exhaustion and flow, in turn, are related to negative and positive WHI, respectively. A series of structured equation modeling (SEM) analyses provided strong evidence for the dual-process model of WHI. The implications for WHI research and practice are discussed.
Going Down?
Authors: McBrier Debra Branch , Wilson George
Published: June 2004

In the 1990s “new” economy, was downward mobility from high-level white-collar occupations related to race, and if so, what factors explain this relationship? We use Panel Study of Income Dynamics data to explore the effect of race on the incidence and process of downward occupational mobility during the 1990s. Findings indicate that, relative to White workers, African Americans suffered a higher incidence of downward occupational mobility, especially to blue-collar destinations, and the process by which African Americans fell down the occupational queue was less strongly predicted by traditional causal factors such as supply-side characteristics and job/labor market characteristics.
Assaultive Behavior in State Psychiatric Hospitals
Authors: Linhorst Donald M. , Scott Lisa Parker
Published: June 2004

Forensic patients are occupying an increasingly large number of beds in state psychiatric hospitals. The presence of these mentally ill offenders has raised concerns about the risk they present to nonforensic patients. This study compared the rate of assaults and factors associated with assaultive behavior among 308 nonforensic patients and two groups of forensic patients including 469 patients found not guilty by reason of insanity and 76 pretrial patients. Consistent with other studies, nonforensic patients had higher rates of assaults than either group of forensic patients. However, being a forensic patient did not affect the odds of assault when controlling for the effects of demographic and clinical variables in a multivariate logistic regression analysis. Factors associated with assaults in each of the three patient groups were identified using multivariate analyses. Implications are presented for treatment of assaultive behavior, mixing of forensic and nonforensic patients within state hospitals, forensic release policies, and future research.
Battered Mothers Who Physically Abuse Their Children
Authors: Coohey Carol
Published: June 2004

The purpose of this study is to understand why some battered mothers physically abuse their children. Mothers who were battered and physically abused their children (the co-occurrence group) were compared with mothers who were neither battered nor physically abused, who were only battered, and who only abused (N = 184). The mothers in the co-occurrence group were more likely than the mothers who did not physically abuse their children to have been severely assaulted by their own mothers as children, have had poorer quality relationships with and receive less support from their mothers, have more stressors, and have known their partners for less time. These differences were not found between the mothers in the co-occurrence and abuse-only groups. In the multivariate analysis, having been assaulted by one’s own mother as a child—not being battered by one’s partner—was the most potent predictor for whether a mother physically abused her child.
Stranger and Acquaintance Sexual Assault of Adult Males
Authors: Stermac Lana , del Bove Giannetta , Addison Mary
Published: June 2004

This study examined victim and assault characteristics and the nature and extent of coercion, violence, and physical injuries among adult male victims of sexual assaults. Client records of three groups presenting to a sexual assault care center were included: males assaulted by a stranger (n = 64), males assaulted by an acquaintance (n = 81), and females assaulted by an acquaintance (n = 106). Study results revealed that male victims of sexual assault tended to be young, single men who reported high rates of vulnerabilities such as homelessness and physical, psychiatric, and cognitive disabilities. Male stranger assailant victims were more likely to experience assaults involving weapons and physical violence. Injuries sustained by victims and services delivered at the sexual assault care center were similar for both male and female clients. The results of this study reveal new information about violence in male sexual assaults and the vulnerability of the male victims.
O Brother, Where are Thou?
Authors: Vaast Emmanuelle
Published: June 2004

Communities of practice are highly situated and, yet, networks of practice supposedly connect them. Assuming the situated dimension of work and identity in communities of practice, how may dispersed agents be connected, and how may the features of communities of practice be extended from the local to the network level? This article proposes that the use of intranets contributes to the interconnections of local communities and to the emergence of a network of practice. It draws on two case studies in which members of local communities used an intranet system to establish communications with remote colleagues in ways that did not merely reproduce their immediate context. The use of the intranet contributed to the mutual reinforcement of local communities, and of the overall network, and to growing complementarities among colleagues at different levels. Conceptually, in a relational perspective, the use of the intranet extended the situatedness of practice.