bluuebunny/crossref_metadata_2025 huggingface dataset:
The chemokine stromal cell‐derived factor‐1/CXCL12 activates the nigrostriatal dopamine system
Authors: Skrzydelski D. , Guyon A. , Daugé V. , Rovère C. , Apartis E. , Kitabgi P. , Nahon J. L. , Rostène W. , Parsadaniantz S. Mélik
Published: May 2007

We recently demonstrated that dopaminergic (DA) neurons of the rat substantia nigra constitutively expressed CXCR4, receptor for the chemokine stromal cell‐derived factor‐1 (SDF‐1)/CXCL12 (SDF‐1). To check the physiological relevance of such anatomical observation, in vitro and in vivo approaches were used. Patch clamp recording of DA neurons in rat substantia nigra slices revealed that SDF‐1 (10 nmol/L) induced: (i) a depolarization and increased action potential frequency; and (ii) switched the firing pattern of depolarized DA neurons from a tonic to a burst firing mode. This suggests that SDF‐1 could increase DA release from neurons. Consistent with this hypothesis, unilateral intranigral injection of SDF‐1 (50 ng) in freely moving rat decreased DA content and increased extracellular concentrations of DA and metabolites in the ipsilateral dorsal striatum, as shown using microdialysis. Furthermore, intranigral SDF‐1 injection induced a contralateral circling behavior. These effects of SDF‐1 were mediated via CXCR4 as they were abrogated by administration of a selective CXCR4 antagonist. Altogether, these data demonstrate that SDF‐1, via CXCR4, activates nigrostriatal DA transmission. They show that the central functions of chemokines are not restricted, as originally thought, to neuroinflammation, but extend to neuromodulatory actions on well‐defined neuronal circuits in non‐pathological conditions.
Roles of extracellular signal‐regulated protein kinases 5 in spinal microglia and primary sensory neurons for neuropathic pain
Authors: Obata Koichi , Katsura Hirokazu , Mizushima Toshiyuki , Sakurai Jun , Kobayashi Kimiko , Yamanaka Hiroki , Dai Yi , Fukuoka Tetsuo , Noguchi Koichi
Published: May 2007

Neuropathic pain that occurs after peripheral nerve injury is poorly controlled by current therapies. Increasing evidence shows that mitogen‐activated protein kinase (MAPK) play an important role in the induction and maintenance of neuropathic pain. Here we show that activation of extracellular signal‐regulated protein kinases 5 (ERK5), also known as big MAPK1, participates in pain hypersensitivity caused by nerve injury. Nerve injury increased ERK5 phosphorylation in spinal microglia and in both damaged and undamaged dorsal root ganglion (DRG) neurons. Antisense knockdown of ERK5 suppressed nerve injury‐induced neuropathic pain and decreased microglial activation. Furthermore, inhibition of ERK5 blocked the induction of transient receptor potential channels and brain‐derived neurotrophic factor expression in DRG neurons. Our results show that ERK5 activated in spinal microglia and DRG neurons contributes to the development of neuropathic pain. Thus, blocking ERK5 signaling in the spinal cord and primary afferents has potential for preventing pain after nerve damage.
DESIGNING INTELLIGENT KNOWLEDGE: EPISTEMOLOGICAL FAITH AND THE DEMOCRATIZATION OF SCIENCE
Authors: Pierce Clayton
Published: May 2007

Abstract In this essay, Clayton Pierce examines the epistemological standpoints of Intelligent Design (ID) and evolutionary science education, focusing specifically on the pedagogical question of how ID and modern science‐based education fail to promote democratic relations in how students learn, think, and associate with science and technology in society. Pierce explores the debate in education between ID and traditional science education that centers on the epistemological assumptions embodied in the modern scientific model. Turning to Bruno Latour’s recent work in the field of science studies, Pierce develops his argument that both expressions of knowledge fail to deliver an adequate theoretical and practical democratic framework for teaching and learning about knowledge systems and technologies in their social, political, and cultural environments.
FREIRE RE‐VIEWED
Authors: Jackson Sue
Published: May 2007

Abstract The work of Paulo Freire is associated with themes of oppression and liberation, and his critical pedagogy is visionary in its attempts to bring about social transformation. Freire has created a theory of education that embeds these issues within social relations that center around both ideological and material domination. In this review essay, Sue Jackson explores three books: Freire’s final work Pedagogy of Indignation; Cesar Augusto Rossatto’s Engaging Paulo Freire’s Pedagogy of Possibility, which attempts to engage Freire’s pedagogy of possibility; and C.A. Bowers and Frederique Apffel‐Marglin’s edited collection Re‐thinking Freire, which asks readers to reconsider Freire’s work in light of globalization and environmental crises. Jackson questions the extent to which Freire’s pedagogical approaches are useful to educators as well as to “the oppressed,” and whether challenges to re‐think Freire can lead to new kinds of critical pedagogies.
APPLYING BAKHTIN SCHOLARSHIP ON DISCOURSE IN EDUCATION: A CRITICAL REVIEW ESSAY
Authors: Matusov Eugene
Published: May 2007

Abstract Recently, Bakhtinian philologists have charged scholars of education with misapplying Bakhtin’s scholarship in their field. In this critical essay, Eugene Matusov reviews two recent edited collections relevant to this issue: Arnetha F. Ball and Sarah Warshauer Freedman’s Bakhtinian Perspectives on Language, Literacy, and Learning and Bonny Norton and Kelleen Toohey’s Critical Pedagogies and Language Learning. He uses these texts to consider whether Bakhtin has been misapplied in education, how and whether Bakhtin’s literary scholarship can be useful for education, and how education can inform Bakhtinian scholarship. Matusov shows that the philologists' critique of educational scholars is grounded but unjustifiably all‐encompassing. Finally, he problematizes whether Bakhtin’s notions of dialogism and internally persuasive discourse are compatible with institutionalized education.
A genetic screen identifies mutations in the yeast WAR1 gene, linking transcription factor phosphorylation to weak‐acid stress adaptation
Authors: Gregori Christa , Bauer Bettina , Schwartz Chantal , Kren Angelika , Schüller Christoph , Kuchler Karl
Published: May 2007

Exposure of the yeast Saccharomyces cerevisiae to weak organic acids such as the food preservatives sorbate, benzoate and propionate leads to the pronounced induction of the plasma membrane ATP‐binding cassette (ABC) transporter, Pdr12p. This protein mediates efflux of weak acid anions, which is essential for stress adaptation. Recently, we identified War1p as the dedicated transcriptional regulator required for PDR12 stress induction. Here, we report the results from a genetic screen that led to the isolation of two war1 alleles encoding mutant variants, War1‐28p and War1‐42p, which are unable to support cell growth in the presence of sorbate. DNA sequencing revealed that War1‐28 encodes a truncated form of the transcriptional regulator, and War1‐42 carries three clustered mutations near the C‐terminal activation domain. Although War1‐42 is expressed and properly localized in the nucleus, the War1‐42p variant fails to bind the weak‐acid‐response elements in the PDR12 promoter, as shown by in vivo footprinting. Importantly, in contrast with wild‐type War1p, War1‐42p is also no longer phosphorylated upon weak‐acid challenge, demonstrating that phosphorylation of War1p, its activation and DNA binding are tightly linked processes that are essential for adaptation to weak‐acid stress.
A REVIEW OF RECENT DEVELOPMENTS IN INTEGRITY TEST RESEARCH
Authors: BERRY CHRISTOPHER M. , SACKETT PAUL R. , WIEMANN SHELLY
Published: May 2007

A sizable body of new literature on integrity tests has appeared since the last review of this literature by Sackett and Wanek (1996). Understanding of the constructs underlying integrity tests continues to grow, aided by new work at the item level. Validation work against a growing variety of criteria continues to be carried out. Work on documenting fakability and coachability continues, as do efforts to increase resistance to faking. New test types continue to be developed. Examination of subgroup differences continues, both at the test and facet level. Research addressing applicant reactions and cross‐cultural issues is also reviewed.
EMOTION HELPERS: THE ROLE OF HIGH POSITIVE AFFECTIVITY AND HIGH SELF‐MONITORING MANAGERS
Authors: TOEGEL GINKA , ANAND N. , KILDUFF MARTIN
Published: May 2007

Who provides help to employees suffering anxiety and emotional pain in organizations? From an interactionist perspective, we anticipated that increasing levels of managerial responsibility would unlock discretionary helping behavior related to differences in self‐monitoring and positive affectivity. Results from a study of 94 members of a recruitment firm confirmed that those active in providing emotional help to others in the workplace tended to possess a combination of managerial responsibility and a high self‐monitoring or high positive affectivity disposition. By contrast, when members were low in positive affect or self‐monitoring they provided less emotional help to others, irrespective of the level of managerial responsibility. These interaction results remained significant after taking into account centrality in friendship and workflow networks, as well as significant effects of gender.
RETEST EFFECTS ON IDENTICAL AND PARALLEL FORMS IN CERTIFICATION AND LICENSURE TESTING
Authors: RAYMOND MARK R. , NEUSTEL SANDRA , ANDERSON DAN
Published: May 2007

Examinees who take credentialing tests and other types of high‐stakes assessments are usually provided an opportunity to repeat the test if they are unsuccessful on initial attempts. To prevent examinees from obtaining unfair score increases by memorizing the content of specific test items, testing agencies usually assign an alternate form to repeat examinees. Given that the use of multiple forms presents both practical and psychometric challenges, it is important to determine if unwarranted score gains occur. Most research indicates that repeat examinees realize score gains when taking the same form twice; however, the research is far from conclusive, particularly within the context of credentialing. For the present investigations, two samples of repeat examinees were randomly assigned to receive either the same test form or a different, but parallel, form on the second occasion. Study 1 found score gains of about 0.79 SD units for 71 examinees who repeated a certification examination in computed tomography. Study 2 found gains of 0.48 SD units for 765 examinees who repeated a radiography certification examination. In both studies score gains for examinees receiving the parallel test were nearly indistinguishable from score gains for those who received the same test. Factors are identified that may influence the generalizability of these findings to other assessment contexts.
Inactivation of inducible nitric oxide synthase protects intestinal pacemaker cells from postoperative damage
Authors: Yanagida Hiroe , Sanders Kenton M. , Ward Sean M.
Published: May 2007

Abdominal surgery causes postoperative gastrointestinal dysmotility which can progress to paralytic ileus. Surgery causes inflammatory responses leading to loss of interstitial cells of Cajal (ICC), which generate intestinal pacemaker activity. Here, we demonstrate that a deficiency in or pharmacological inhibition of inducible nitric oxide synthase (iNOS) before surgery protects ICC from postoperative damage. Ileal segments from wild‐type, iNOS and cyclooxygenase‐2 (COX‐2) knockout mice were resected and reconstructions were performed by end‐to‐end anastomoses. Wild‐type animals were exposed to iNOS inhibitors before surgery, and electrical activity and ICC were examined 5 h after surgery. Intestinal surgery on wild‐type mice caused a significant reduction in ICC and pacemaking at distances up to 5 cm from the anastomosis site. ICC networks and pacemaking were protected in iNOS−/− mice. In animals treated preoperatively with iNOS inhibitors, pacemaker activity was depressed only at the anastomosis site. COX‐2 deficiency also muted postoperative disruption in pacemaker activity. Postoperative surgical damage consists of a local response and a more widespread response in which ICC and pacemaker activity are disrupted. Damage to ICC and pacemaking was greatly attenuated in the absence of NO derived from iNOS. Thus, management of iNOS expression or activity prior to intestinal surgery protects against postsurgical dysmotility and reduces the severity of postoperative ileus.
KATP channel deficiency in mouse flexor digitorum brevis causes fibre damage and impairs Ca2+ release and force development during fatigue in vitro
Authors: Cifelli Carlo , Bourassa François , Gariépy Louise , Banas Krystyna , Benkhalti Maria , Renaud Jean‐Marc
Published: May 2007

Activation of the KATP channels results in faster fatigue rates as the channels depress action potential amplitude, whereas abolishing the channel activity has no effect in whole extensor digitorum longus (EDL) and soleus muscles. In this study, we examined the effects of abolished KATP channel activity during fatigue at 37°C on free intracellular Ca2+(Ca2+i) and tetanic force using single muscle fibres and small muscle bundles from the flexor digitorum brevis (FDB). KATP channel deficient muscle fibres were obtained (i) pharmacologically by exposing wild‐type fibres to glibenclamide, and (ii) genetically using null mice for the Kir6.2 gene (Kir6.2−/− mice). Fatigue was elicited using 200 ms tetanic contractions every second for 3 min. This study demonstrated for the first time that abolishing KATP channel activity at 37°C resulted in faster fatigue rates, where decreases in peak Ca2+i and tetanic force were faster in KATP channel deficient fibres than in control wild‐type fibres. Furthermore, several contractile dysfunctions were also observed in KATP channel deficient muscle fibre. They included partially or completely supercontracted single muscle fibres, greater increases in unstimulated Ca2+i and unstimulated force, and lower force recovery. We propose that the observed faster rate of fatigue in KATP channel deficient fibres is because the decreases in peak Ca2+i and force caused by contractile dysfunctions prevail over the expected slower decreases when the channels do not depress action potential amplitude.
A‐type potassium channels differentially tune afferent pathways from rat solitary tract nucleus to caudal ventrolateral medulla or paraventricular hypothalamus
Authors: Bailey T. W. , Hermes S. M. , Whittier K. L. , Aicher S. A. , Andresen M. C.
Published: May 2007

The solitary tract nucleus (NTS) conveys visceral information to diverse central networks involved in homeostatic regulation. Although afferent information content arriving at various CNS sites varies substantially, little is known about the contribution of processing within the NTS to these differences. Using retrograde dyes to identify specific NTS projection neurons, we recently reported that solitary tract (ST) afferents directly contact NTS neurons projecting to caudal ventrolateral medulla (CVLM) but largely only indirectly contact neurons projecting to the hypothalamic paraventricular nucleus (PVN). Since intrinsic properties impact information transmission, here we evaluated potassium channel expression and somatodendritic morphology of projection neurons and their relation to afferent information output directed to PVN or CVLM pathways. In slices, tracer‐identified projection neurons were classified as directly or indirectly (polysynaptically) coupled to ST afferents by EPSC latency characteristics (directly coupled, jitter < 200 μs). In each neuron, voltage‐dependent potassium currents (IK) were evaluated and, in representative neurons, biocytin‐filled structures were quantified. Both CVLM‐ and PVN‐projecting neurons had similar, tetraethylammonium‐sensitive IK. However, only PVN‐projecting NTS neurons displayed large transient, 4aminopyridine‐sensitive, A‐type currents (IKA). PVN‐projecting neurons had larger cell bodies with more elaborate dendritic morphology than CVLM‐projecting neurons. ST shocks faithfully (> 75%) triggered action potentials in CVLM‐projecting neurons but spike output was uniformly low (< 20%) in PVN‐projecting neurons. Pre‐conditioning hyperpolarization removed IKA inactivation and attenuated ST‐evoked spike generation along PVN but not CVLM pathways. Thus, multiple differences in structure, organization, synaptic transmission and ion channel expression tune the overall fidelity of afferent signals that reach these destinations.
Contribution of α2‐adrenoceptors and Y1 neuropeptide Y receptors to the blunting of sympathetic vasoconstriction induced by systemic hypoxia in the rat
Authors: Coney Andrew M. , Marshall Janice M.
Published: May 2007

There is evidence that sympathetically evoked vasoconstriction in skeletal muscle is blunted in systemic hypoxia, but the mechanisms underlying this phenomenon are not clear. In Saffan‐anaesthetized Wistar rats, we have studied the role of α2‐adrenoceptors and neuropeptide Y (NPY) Y1 receptors in mediating vasoconstriction evoked by direct stimulation of the lumbar sympathetic chain by different patterns of impulses in normoxia (N) and systemic hypoxia (H: breathing 8% O2). Patterns comprised 120 impulses delivered in bursts over a 1 min period at 40 or 20 Hz, or continuously at 2 Hz. Hypoxia attenuated the evoked increases in femoral vascular resistance (FVR) by all patterns, the response to 2 Hz being most affected (40 Hz bursts: N = 3.25 ± 0.75 arbitrary resistance units (RU); H = 1.14 ± 0.29 RU). Yohimbine (Yoh, α2‐adrenoceptor antagonist) or BIBP 3226 (Y1‐receptor antagonist) did not affect baseline FVR. In normoxia, Yoh attenuated the responses evoked by high frequency bursts and 2 Hz, whereas BIBP 3226 only attenuated the response to 40 Hz (40 Hz bursts: N + Yoh = 2.1 ± 0.59 RU; N + BIBP 3226 = 1.9 ± 0.4 RU). In hypoxia, Yoh did not further attenuate the evoked responses, but BIBP 3226 further attenuated the response to 40 Hz bursts. These results indicate that neither α2‐adrenoceptors nor Y1 receptors contribute to basal vascular tone in skeletal muscle, but both contribute to constrictor responses evoked by high frequency bursts of sympathetic activity. We propose that in systemic hypoxia, the α2‐mediated component represents about 50% of the sympathetically evoked constriction that is blunted, whereas the contribution made by Y1 receptors is resistant. Thus we suggest the importance of NPY in the regulation of FVR and blood pressure increases during challenges such as systemic hypoxia.
Protein kinase A is activated by the n–3 polyunsaturated fatty acid eicosapentaenoic acid in rat ventricular muscle
Authors: Szentandrássy Norbert , Pérez‐Bido M. R. , Alonzo E. , Negretti N. , O'Neill Stephen C.
Published: May 2007

During cardiac ischaemia antiarrhythmic n–3 polyunsaturated fatty acids (PUFAs) are released following activation of phospholipase A2, if they are in the diet prior to ischaemia. Here we show a positive lusitropic effect of one such PUFA, eicosapentaenoic acid (EPA) in the antiarrhythmic concentration range in Langendorff hearts and isolated rat ventricular myocytes due to activation of protein kinase A (PKA). Several different approaches indicated activation of PKA by EPA (5–10 μmol l−1): the time constant of decay of the systolic Ca2+ transient decreased to 65.3 ± 5.0% of control, Western blot analysis showed a fourfold increase in phospholamban phosphorylation, and PKA activity increased by 21.0 ± 7.3%. In addition myofilament Ca2+ sensitivity was reduced in EPA; this too may have resulted from PKA activation. We also found that EPA inhibited L‐type Ca2+ current by 38.7 ± 3.9% but this increased to 63.3 ± 3.4% in 10 μmol l−1 H89 (to inhibit PKA), providing further evidence of activation of PKA by EPA. PKA inhibition also prevented the lusitropic effect of EPA on the systolic Ca2+ transient and contraction. Our measurements show, however, PKA activation in EPA cannot be explained by increased cAMP levels and alternative mechanisms for PKA activation are discussed. The combined lusitropic effect and inhibition of contraction by EPA may, respectively, combat diastolic dysfunction in ischaemic cardiac muscle and promote cell survival by preserving ATP. This is a further level of protection for the heart in addition to the well‐documented antiarrhythmic qualities of these fatty acids.
Task‐related changes in propriospinal excitation from hand muscles to human flexor carpi radialis motoneurones
Authors: Iglesias Caroline , Marchand‐Pauvert Véronique , Lourenço George , Burke David , Pierrot‐Deseilligny Emmanuel
Published: May 2007

This study addresses whether there is excitation from human hand muscles to flexor carpi radialis (FCR) motoneurones mediated through propriospinal circuits and, if so, whether it is used in specific motor tasks. Electrical stimuli to the ulnar nerve at wrist level produced an excitation in FCR motoneurones with characteristics typical of a propriospinally mediated effect: low threshold (0.6 × motor threshold (MT)), a group I effect that was not reproduced by purely cutaneous stimuli, long central delay (4.1 ± 0.4 ms in single units), suppression when the stimulus intensity was increased, and facilitation of the corticospinal excitation at the premotoneuronal level. Ulnar‐induced propriospinally mediated excitation was compared during selective voluntary contractions of the FCR and, at equivalent level of FCR EMG, during tasks in which the FCR was activated automatically in postural contractions rather than voluntarily (grip, pinching and pointing). The excitation was significantly greater during grip (and pinching) than during voluntary FCR contractions and pointing, whether measured in single motor units or tonic EMG activity, or whether the response to motor cortex stimulation was assessed as the compound motor‐evoked potential or the corticospinal peak in single units. The discrepancy between the tasks appeared with ulnar intensities above 0.8 × MT and was then present across a wide range of stimulus intensities. This suggests a reduction in the corticospinal control of ‘feedback inhibitory interneurones’ mediating peripheral inhibition to propriospinal neurones during grip and pinching. The resulting more effective background excitation of propriospinal neurones by the peripheral input from hand muscles could contribute to stabilizing the wrist during grip.
Remodelling of the SUR–Kir6.2 interface of the KATP channel upon ATP binding revealed by the conformational blocker rhodamine 123
Authors: Hosy Eric , Dérand Renaud , Revilloud Jean , Vivaudou Michel
Published: May 2007

ATP‐sensitive K+ channels (KATP channels) are metabolic sensors formed by association of a K+ channel, Kir6, and an ATP‐binding cassette (ABC) protein, SUR, which allosterically regulates channel gating in response to nucleotides and pharmaceutical openers and blockers. How nucleotide binding to SUR translates into modulation of Kir6 gating remains largely unknown. To address this issue, we have used a novel conformational KATP channel inhibitor, rhodamine 123 (Rho123) which targets the Kir6 subunit in a SUR‐dependent manner. Rho123 blocked SUR‐less Kir6.2 channels with an affinity of ∼1 μm, regardless of the presence of nucleotides, but it had no effect on channels formed by the association of Kir6.2 and the N‐terminal transmembrane domain TMD0 of SUR. Rho123 blocked SUR + Kir6.2 channels with the same affinity as Kir6.2 but this effect was antagonized by ATP. Protection from Rho123 block by ATP was due to direct binding of ATP to SUR and did not entail hydrolysis because it was not mimicked by AMP, did not require Mg2+ and was reduced by mutations in the nucleotide‐binding domains of SUR. These results suggest that Rho123 binds at the TMD0–Kir6.2 interface and that binding of ATP to SUR triggers a change in the structure of the contact zone between Kir6.2 and domain TMD0 of SUR that causes masking of the Rho123 site on Kir6.2.
ATP is the predominant sympathetic neurotransmitter in rat mesenteric arteries at high pressure
Authors: Rummery Nicole M. , Brock James A. , Pakdeechote Poungrat , Ralevic Vera , Dunn William R.
Published: May 2007

Most studies of neurovascular transmission in isolated small mesenteric arteries have used either isometric recording techniques or measured vasoconstriction in vessels with no distending pressure. Here we have used pressure myography to assess the contribution of noradrenaline and ATP to sympathetic neurotransmission in rat second‐order mesenteric arteries. In arteries pressurized to 30 or 90 mmHg, activation of sympathetic axons with trains of electrical stimuli (50 pulses, 0.5–10 Hz) evoked frequency‐dependent vasoconstrictions that increased in amplitude at higher pressure. In the presence of the P2‐receptor antagonist suramin (0.1 mm), the amplitude of vasoconstrictions to trains at 2 and 10 Hz did not differ at 30 and 90 mmHg. In contrast, in the presence of the α1‐adrenoceptor antagonist prazosin (0.1 μm) vasoconstrictions at 90 mmHg were larger than those at 30 mmHg. At both pressures, the combination of prazosin and suramin virtually abolished constrictions. The purinergic component of vasoconstriction (prazosin‐resistant) was almost abolished by the L‐type Ca2+ channel antagonist nifedipine (1 μm). Increasing pressure from 30 to 90 mmHg decreased the resting membrane potential and increased the amplitude of purinergic excitatory junction potentials. These findings indicate that the contribution of ATP to neurovascular transmission increases when the pressure is raised from 30 to 90 mmHg, which is similar to the pressure second‐order mesenteric arteries experience in vivo, and that Ca2+ influx through L‐type Ca2+ channels is largely responsible for purinergic activation of the vascular smooth muscle.
Two cAMP‐dependent pathways differentially regulate exocytosis of large dense‐core and small vesicles in mouse β‐cells
Authors: Hatakeyama Hiroyasu , Takahashi Noriko , Kishimoto Takuya , Nemoto Tomomi , Kasai Haruo
Published: May 2007

It has been reported that cAMP regulates Ca2+‐dependent exocytosis via protein kinase A (PKA) and exchange proteins directly activated by cAMP (Epac) in neurons and secretory cells. It has, however, never been clarified how regulation of Ca2+‐dependent exocytosis by cAMP differs depending on the involvement of PKA and Epac, and depending on two types of secretory vesicles, large dense‐core vesicles (LVs) and small vesicles (SVs). In this study, we have directly visualized Ca2+‐dependent exocytosis of both LVs and SVs with two‐photon imaging in mouse pancreatic β‐cells. We found that marked exocytosis of SVs occurred with a time constant of 0.3 s, more than three times as fast as LV exocytosis, on stimulation by photolysis of a caged‐Ca2+ compound. The diameter of SVs was identified as ∼80 nm with two‐photon imaging, which was confirmed by electron‐microscopic investigation with photoconversion of diaminobenzidine. Calcium‐dependent exocytosis of SVs was potentiated by the cAMP‐elevating agent forskolin, and the potentiating effect was unaffected by antagonists of PKA and was mimicked by the Epac‐selective agonist 8‐(4‐chlorophenylthio)‐2′‐O‐methyl cAMP, unlike that on LVs. Moreover, high‐glucose stimulation induced massive exocytosis of SVs in addition to LVs, and photolysis of caged cAMP during glucose stimulation caused potentiation of exocytosis with little delay for SVs but with a latency of 5 s for LVs. Thus, Epac and PKA selectively regulate exocytosis of SVs and LVs, respectively, in β‐cells, and Epac can regulate exocytosis more rapidly than PKA.
Dendritic Ca2+ signalling due to activation of α7‐containing nicotinic acetylcholine receptors in rat hippocampal neurons
Authors: Fayuk Dmitriy , Yakel Jerrel L.
Published: May 2007

Neuronal nicotinic acetylcholine receptors (nAChRs) are in the superfamily of Cys‐loop ligand‐gated ion channels, which are widely expressed in the brain. Among the many different subtypes of nAChRs known to be expressed in the rat brain, the α7‐containing nAChRs are considered to be the most permeable to Ca2+. Utilizing highly localized and rapid iontophoretic agonist delivery, combined with patch‐clamp electrophysiology and fura‐2 fluorescence imaging techniques, we examined the α7 nAChR‐mediated currents and [Ca2+]i transients in the dendrites of rat hippocampal CA1 interneurons in the slice. We found that in the dendrites, whereas the amplitudes of the current responses were smaller and the decay kinetics faster than the responses in the soma, the amplitudes of the [Ca2+]i signals were significantly larger. Cultured hippocampal neurons were studied since the dendritic field lies in the same focal plane, which allowed for a broader investigation of the spatiotemporal dynamics of [Ca2+]i signalling. In cultured neurons, the [Ca2+]i signals in the dendrites were similar to those in slices. Interestingly in cultures, even though the amplitude of the α7 nAChR‐mediated currents dramatically decreased with distance from the soma (from ∼20–250 μm), the amplitude of the [Ca2+]i signals did not correlate with distance. This indicates that the relative efficacy of α7 nAChR activation to increase [Ca2+]i levels in dendrites increased severalfold with distance from the soma. These results may have implications for the role that α7 nAChRs have in regulating various signal transduction cascades, synaptic plasticity, and memory processes, via significant changes in [Ca2+]i levels.
Arbitrary Periodic Motions and Grazing Switching of a Forced Piecewise Linear, Impacting Oscillator
Authors: Luo Albert C. J. , Chen Lidi
Published: May 2007

The grazing bifurcation and periodic motion switching of the harmonically forced, piecewise linear system with impacting are investigated. The generic mappings relative to the discontinuous boundaries of this piecewise system are introduced. Based on such mappings, the corresponding grazing conditions are obtained. The mapping structures are developed for the analytical prediction of periodic motions in such a system. The local stability and bifurcation conditions for specified periodic motions are obtained. The regular and grazing, periodic motions are illustrated. The grazing is the origin of the periodic motion switching for this system. Such a grazing bifurcation cannot be estimated through the local stability analysis. This model is applicable to prediction of periodic motions in nonlinear dynamics of gear transmission systems.
Development of a Technique to Locate and Quantify a Crack in a Beam Based on Modal Parameters
Authors: Karthikeyan M. , Tiwari R. , Talukdar S.
Published: May 2007

A model-based algorithm has been developed, in order to locate and quantify the size of a crack, based on free vibration measurements of a cracked beam. Measured natural frequencies (at least two) and corresponding mode shapes of the cracked beam are used in the identification algorithm. The Euler–Bernoulli beam theory is used to model the beam. The crack of the beam is modeled through standard five crack flexibility coefficients, by considering bending effects only. Damping is assumed to be Rayleigh’s damping. The finite element method is used in the simulation of the cracked beam. The present algorithm is iterative in nature and the iterations are carried out until the estimated and assumed crack depth ratios (as well as its location) become close up to the desired accuracy. The applicability of the algorithm has been tested through numerical examples and is found to be adequate even in the presence of the measurement noise in modes shapes and measurement errors in natural frequencies.
Effect of Tangential Dither Signal on Friction Induced Oscillations in an SDOF Model
Authors: Michaux Michael A. , Ferri Aldo A. , Cunefare Kenneth A.
Published: May 2007

This work examines how friction-induced oscillations in a traditional mass-on-a-moving-belt system are affected by high-frequency excitations, commonly referred to as dither signals. Two different friction laws are considered: a Stribeck friction law governed by a relationship that is cubic in the slip velocity, and an exponentially-based friction law that steadily decreases with slip velocity. Although in both cases the friction force has an initial negative slope versus relative velocity, their stability characteristics are quite different. In particular, it is shown that tangential dither can either stabilize or destabilize an initially stable system, depending on the nature of the friction law, and on other system and dither parameters. The behavior of the systems is studied through use of an averaging technique and through direct numerical simulation. The numerical study validates the stability predictions from the averaging method, and quantifies the partial-cancellation performance of tangential dither.
Parametric Identification of Nonlinear Systems Using Chaotic Excitation
Authors: Narayanan M. D. , Narayanan S. , Padmanabhan Chandramouli
Published: May 2007

The use of a time series, which is the chaotic response of a nonlinear system, as an excitation for the parametric identification of single-degree-of-freedom nonlinear systems is explored in this paper. It is assumed that the system response consists of several unstable periodic orbits, similar to the input, and hence a Fourier series based technique is used to extract these nearly periodic orbits. Criteria to extract these orbits are developed and a least-squares problem for the identification of system parameters is formulated and solved. The effectiveness of this method is illustrated on a system with quadratic damping and a system with Duffing nonlinearity.
On Global Transversality and Chaos in Two-Dimensional Nonlinear Dynamical Systems
Authors: Luo Albert C. J.
Published: May 2007

In this paper, the global transversality and tangency in two-dimensional nonlinear dynamical systems are discussed, and the exact energy increment function (L-function) for such nonlinear dynamical systems is presented. The Melnikov function is an approximate expression of the exact energy increment. A periodically forced, damped Duffing oscillator with a separatrix is investigated as a sampled problem. The corresponding analytical conditions for the global transversality and tangency to the separatrix are derived. Numerical simulations are carried out for illustrations of the analytical conditions. From analytical and numerical results, the simple zero of the energy increment (or the Melnikov function) may not imply that chaos exists. The conditions for the global transversality and tangency to the separatrix may be independent of the Melnikov function. Therefore, the analytical criteria for chaotic motions in nonlinear dynamical systems need to be further developed. The methodology presented in this paper is applicable to nonlinear dynamical systems without any separatrix.
Model Reduction of Systems With Localized Nonlinearities
Authors: Segalman Daniel J.
Published: May 2007

An approach to development of reduced order models for systems with local nonlinearities is presented. The key of this approach is the augmentation of conventional basis functions with others having appropriate discontinuities at the locations of nonlinearity. A Galerkin solution using the above combination of basis functions appears to capture the dynamics of the system very efficiently—employing small basis sets. This method is particularly useful for problems of structural dynamics, but may have application in other fields as well. For problems involving small amplitude dynamics, when one employs as a basis the eigenmodes of a reference linear system plus the discontinuous (joint) modes, the resulting predictions, though still nonlinear, are approximated well as linear combinations of the eigenmodes. This is in good agreement with the experimental observation that jointed structures, though demonstrably nonlinear, manifest kinematics that are well described using eigenmodes of a corresponding system where the joints are replaced by linear springs.
On the Bifurcation Pattern and Normal Form in a Modified Predator–Prey Nonlinear System
Authors: Ghosh Dibakar , Chowdhury A. Roy
Published: May 2007

Detailed bifurcation pattern and stability structure is studied in a modified predator–prey system, with nonmonotonic response function. It is observed that almost all the parameters of the system have a positive influence as far as bifurcation is concerned. The analysis is done with the help of the package MATCONT. In the second stage of the analysis the detailed structure of the normal form is obtained after the corresponding position of Hopf bifurcation and Bogdanov–Takens bifurcation are identified with the help of a modified approach recently proposed by Kuznetsov (1995, Elements of Bifurcation Theory, Springer, New York, Chap. 8). It is important to note that the positions of Hopf and Bogdanov–Taken bifurcation as obtained from the analytic studies in this approach coincides exactly with those obtained from MATCONT.
Nonlinear Vibrations of Viscoelastic Composite Cylindrical Panels
Authors: Eshmatov Bakhtiyor , Mukherjee Subrata
Published: May 2007

This paper is devoted to mathematical models of problems of nonlinear vibrations of viscoelastic, orthotropic, and isotropic cylindrical panels. The models are based on Kirchhoff-Love hypothesis and Timoshenko generalized theory (including shear deformation and rotatory inertia) in a geometrically nonlinear statement. A choice of the relaxation kernel with three rheological parameters is justified. A numerical method based on the use of quadrature formulas for solving problems in viscoelastic systems with weakly singular kernels of relaxation is proposed. With the help of the Bubnov-Galerkin method in combination with a numerical method, the problems in nonlinear vibrations of viscoelastic orthotropic and isotropic cylindrical panels are solved using the Kirchhoff-Love and Timoshenko hypothesis. Comparisons of the results obtained by these theories, with and without taking elastic waves propagation into account, are presented. In all problems, the convergence of Bubnov-Galerkin’s method has been investigated. The influences of the viscoelastic and anisotropic properties of a material, on the process of vibration, are discussed in this work.
Applying Sherman-Morrison-Woodbury Formulas to Analyze the Free and Forced Responses of a Linear Structure Carrying Lumped Elements
Authors: Cha Philip D. , Yoder Nathanael C.
Published: May 2007

A simple approach is proposed that can be used to analyze the free and forced responses of a combined system, consisting of an arbitrarily supported continuous structure carrying any number of lumped attachments. The assumed modes method is utilized to formulate the equations of motion, which conveniently leads to a form that allows one to exploit the Sherman-Morrison or the Sherman-Morrison-Woodbury formulas to compute the natural frequencies and frequency response of the combined system. Rather than solving a generalized eigenvalue problem to obtain the natural frequencies of the system, a frequency equation is formulated whose solution can be easily solved either numerically or graphically. In order to determine the response of the structure to a harmonic input, a method is formulated that leads to a reduced matrix whose inverse yields the same result as the traditional method, which requires the inversion of a larger matrix. The proposed scheme is easy to code, computationally efficient, and can be easily modified to accommodate arbitrarily supported continuous linear structures that carry any number of miscellaneous lumped attachments.
Wind Tunnel Test on Cable Dome of Geiger Type
Authors: Zhang Zhi-hong , Tamura Yukio
Published: May 2007

This paper presents preliminary results of an aeroelastic wind tunnel test on a cable dome. The structural design of the model is given in detail. Similarity requirements based on dimensional analysis are discussed, including Froude number, Cauchy number, and Scruton number. Structural tests are conducted on the aeroelastic model. Dynamic instability subject to harmonic excitation like a single-degree-of-freedom hardening system is verified. Both odd and even frequency components are excited when the shaking table shakes at 29Hz. For the one-degree-of-freedom Duffing model, even frequency components will be impossible due to the symmetry of the motion equation if symmetry-breaking bifurcation behaviors do not occur. Phase plane is checked and discussed when the shaking table shakes at 7Hz. A strange attractor appears to exist on the basis of the Poincare map. Some statistical results of wind tunnel tests are presented. The possibility of aeroelastic instability of the cable dome is discussed.
Prediction of Dry-Friction Whirl and Whip Between a Rotor and a Stator
Authors: Childs Dara W. , Bhattacharya Avijit
Published: May 2007

This paper addresses recent test results for dry-friction whip and whirl. Authors of these publications suggest that predictions from Black’s 1968 paper (J. Mech. Eng. Sci., 10(1), pp. 1–12) are deficient in predicting their observed transition speeds from whirl to whip and the associated precession frequencies of whirl and whip motion. Predictions from Black’s simple Jeffcott-rotor/point-mass stator are cited. This model is extended here to a multimode rotor and stator model with an arbitrary axial location for rotor-stator rubbing. Predictions obtained from this new model are quite close to experimental observations in terms of the transition from whip to whirl and observed precession frequencies. Paradoxically, nonlinear numerical simulations using Black’s model fail to produce the whirl and whip solutions. The Coulomb friction force in Black’s model has a fixed direction, and Bartha showed in 2000 (“Dry Friction Backward Whirl of Rotors,” Dissertation, THE No. 13817, ETH Zurich) that by making the friction-force direction depend on the relative sliding velocity, nonlinear simulations would produce the predicted whirl solutions. He also showed that Black’s proposed whip solution at the upper precession-frequency transition from whirl to whip was unstable. The multimode extension of Black’s model predicts a complicated range of whirl and whip possibilities; however, nonlinear time-transient simulations (including the sgn function definition for the Coulomb force) only produce the initial whirl precession range, initial whirl-whip transition, and initial whip frequency. Simulation results for these values agree well with predictions. However, none of the predicted higher-frequency whirl results are obtained. Also, the initial whip frequency persists to quite high running speeds and does not (as predicted) transition to higher frequencies. Hence, despite its deficiencies, correct and very useful predictions are obtained from a reasonable extension of Black’s model.
Saturation of the Southern Ocean CO
2
Sink Due to Recent Climate Change
Authors: Le Quéré Corinne , Rödenbeck Christian , Buitenhuis Erik T. , Conway Thomas J. , Langenfelds Ray , Gomez Antony , Labuschagne Casper , Ramonet Michel , Nakazawa Takakiyo , Metzl Nicolas , Gillett Nathan , Heimann Martin
Published: May 2007

Based on observed atmospheric carbon dioxide (CO
2
) concentration and an inverse method, we estimate that the Southern Ocean sink of CO
2
has weakened between 1981 and 2004 by 0.08 petagrams of carbon per year per decade relative to the trend expected from the large increase in atmospheric CO
2
. We attribute this weakening to the observed increase in Southern Ocean winds resulting from human activities, which is projected to continue in the future. Consequences include a reduction of the efficiency of the Southern Ocean sink of CO
2
in the short term (about 25 years) and possibly a higher level of stabilization of atmospheric CO
2
on a multicentury time scale.
Eddy/Wind Interactions Stimulate Extraordinary Mid-Ocean Plankton Blooms
Authors: McGillicuddy Dennis J. , Anderson Laurence A. , Bates Nicholas R. , Bibby Thomas , Buesseler Ken O. , Carlson Craig A. , Davis Cabell S. , Ewart Courtney , Falkowski Paul G. , Goldthwait Sarah A. , Hansell Dennis A. , Jenkins William J. , Johnson Rodney , Kosnyrev Valery K. , Ledwell James R. , Li Qian P. , Siegel David A. , Steinberg Deborah K.
Published: May 2007

Episodic eddy-driven upwelling may supply a significant fraction of the nutrients required to sustain primary productivity of the subtropical ocean. New observations in the northwest Atlantic reveal that, although plankton blooms occur in both cyclones and mode-water eddies, the biological responses differ. Mode-water eddies can generate extraordinary diatom biomass and primary production at depth, relative to the time series near Bermuda. These blooms are sustained by eddy/wind interactions, which amplify the eddy-induced upwelling. In contrast, eddy/wind interactions dampen eddy-induced upwelling in cyclones. Carbon export inferred from oxygen anomalies in eddy cores is one to three times as much as annual new production for the region.
Embodying Emotion
Authors: Niedenthal Paula M.
Published: May 2007

Recent theories of embodied cognition suggest new ways to look at how we process emotional information. The theories suggest that perceiving and thinking about emotion involve perceptual, somatovisceral, and motoric reexperiencing (collectively referred to as “embodiment”) of the relevant emotion in one's self. The embodiment of emotion, when induced in human participants by manipulations of facial expression and posture in the laboratory, causally affects how emotional information is processed. Congruence between the recipient's bodily expression of emotion and the sender's emotional tone of language, for instance, facilitates comprehension of the communication, whereas incongruence can impair comprehension. Taken all together, recent findings provide a scientific account of the familiar contention that “when you're smiling, the whole world smiles with you.”
Conformational Switching in the Fungal Light Sensor Vivid
Authors: Zoltowski Brian D. , Schwerdtfeger Carsten , Widom Joanne , Loros Jennifer J. , Bilwes Alexandrine M. , Dunlap Jay C. , Crane Brian R.
Published: May 2007

The
Neurospora crassa
photoreceptor Vivid tunes blue-light responses and modulates gating of the circadian clock. Crystal structures of dark-state and light-state Vivid reveal a light, oxygen, or voltage Per-Arnt-Sim domain with an unusual N-terminal cap region and a loop insertion that accommodates the flavin cofactor. Photoinduced formation of a cystein-flavin adduct drives flavin protonation to induce an N-terminal conformational change. A cysteine-to-serine substitution remote from the flavin adenine dinucleotide binding site decouples conformational switching from the flavin photocycle and prevents Vivid from sending signals in
Neurospora
. Key elements of this activation mechanism are conserved by other photosensors such as White Collar-1, ZEITLUPE, ENVOY, and flavin-binding, kelch repeat, F-BOX 1 (FKF1).
RNA Maps Reveal New RNA Classes and a Possible Function for Pervasive Transcription
Authors: Kapranov Philipp , Cheng Jill , Dike Sujit , Nix David A. , Duttagupta Radharani , Willingham Aarron T. , Stadler Peter F. , Hertel Jana , Hackermüller Jörg , Hofacker Ivo L. , Bell Ian , Cheung Evelyn , Drenkow Jorg , Dumais Erica , Patel Sandeep , Helt Gregg , Ganesh Madhavan , Ghosh Srinka , Piccolboni Antonio , Sementchenko Victor , Tammana Hari , Gingeras Thomas R.
Published: May 2007

Significant fractions of eukaryotic genomes give rise to RNA, much of which is unannotated and has reduced protein-coding potential. The genomic origins and the associations of human nuclear and cytosolic polyadenylated RNAs longer than 200 nucleotides (nt) and whole-cell RNAs less than 200 nt were investigated in this genome-wide study. Subcellular addresses for nucleotides present in detected RNAs were assigned, and their potential processing into short RNAs was investigated. Taken together, these observations suggest a novel role for some unannotated RNAs as primary transcripts for the production of short RNAs. Three potentially functional classes of RNAs have been identified, two of which are syntenically conserved and correlate with the expression state of protein-coding genes. These data support a highly interleaved organization of the human transcriptome.