bluuebunny/crossref_metadata_2025_split huggingface dataset:
Midbrain muscarinic receptor mechanisms underlying regulation of mesoaccumbens and nigrostriatal dopaminergic transmission in the rat
Authors: Miller Anthony D. , Blaha Charles D. 
Published: May 2005

AbstractLaterodorsal (LDT) and pedunculopontine (PPT) tegmental nuclei in the mesopontine project cholinergic inputs to the midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc), respectively, to directly and indirectly influence the activity of dopamine neuronal cells via actions on muscarinic and nicotinic receptors. The present study investigated the role of midbrain muscarinic receptors in the functional modulation of VTA and SNc dopamine cell activity as reflected by alterations in, respectively, nucleus accumbens (NAc) and striataldopamine efflux. In vivo chronoamperometry was used to measure changes in basal dopamine efflux via stearate–graphite paste electrodes implanted unilaterally in the NAc or striatum of urethane‐anaesthetized rats, following blockade or activation of, respectively, VTA or SNc muscarinic receptors. Intra‐VTA or ‐SNc infusion of the muscarinic antagonist scopolamine (200 µg/µL) reduced, respectively, NAc and striatal dopamine efflux while infusion of the muscarinic and nicotinic agonist carbachol (0.5 µg/µL) or the prototypical muscarinic agonist muscarine (0.5 µg/µL) increased NAc and striatal dopamine efflux. Transient decreases in dopamine efflux preceded these increases selectively in the striatum, suggesting a reduction in excitatory or increase in inhibitory drive to the SNc by preferential activation of M3 muscarinic receptors on GABA interneurons and glutamatergic inputs. This was confirmed by showing that selective blockade of M3 receptors with p‐F‐HHSiD (0.5 µg/µL) increased striatal, but not NAc, dopamine efflux. Together, these findings suggest that midbrain muscarinic receptors, probably M5 subtypes on VTA and SNc dopamine neurons, contribute to the tonic excitatory regulation of forebrain basal dopamine transmission whereas presynaptic M3 receptors serve to counter excessive excitation of nigral dopamine cell activity.
A role for norepinephrine in the regulation of context‐dependent ZENK expression in male zebra finches (Taeniopygia guttata)
Authors: Castelino Christina B. , Ball Gregory F. 
Published: May 2005

AbstractSinging drives expression of the immediate‐early gene ZENK in a context‐dependent manner in certain nuclei within the avian song circuit of male zebra finches (Taeniopygia guttata). ZENK mRNA expression is low when males are engaged in female‐ or male‐directed song, but high during solo song. Neurotransmitter systems like catecholamines with diffuse projections to forebrain regions are good candidates for regulation of such context‐dependent brain activity. We investigated whether the noradrenergic system regulates the dramatic switch in ZENK expression across contexts in male zebra finches. We systemically injected a noradrenergic neurotoxin N‐(2‐chloroethyl)‐N‐ethyl‐2‐bromobenzylamine hydrochloride (DSP‐4) and found a marked increase in the resultant ZENK expression in area X of the medial striatum in male zebra finches singing directed song. ZENK protein expression in saline‐treated males across different contexts mirrored the pattern of previously reported ZENK mRNA expression. We corroborated DSP‐4 specificity via immunohistochemical procedures for tyrosine hydroxylase and dopamine‐beta hydroxylase, which revealed decreases in norepinephrine synthesizing nuclei and certain song control nuclei. Based on these results we propose a mechanism by which the noradrenergic system usually downregulates ZENK expression in area X during directed song. By depleting this system we induced a disruption of this regulation and reversion back to the default situation characterized by an increase in motor‐driven ZENK expression in the song circuit. These data demonstrate that the noradrenergic system (probably in concert with other modulatory neurotransmitters) plays an important role in the response of the brain to salient events that occur in the context of a natural behavior − singing.
Opposite effects of tetanic stimulation of the auditory thalamus or auditory cortex on the acoustic startle reflex in awake rats
Authors: Huang Juan , Wu Xihong , Yeomans John , Li Liang 
Published: May 2005

AbstractThe amygdala mediates both emotional learning and fear potentiation of startle. The lateral amygdala nucleus (LA) receives auditory inputs from both the auditory thalamus (medial geniculate nucleus; MGN) and auditory association cortex (AAC), and is critical for auditory fear conditioning. The central amygdala nucleus, which has intra‐amygdaloid connections with LA, enhances startle magnitude via midbrain connections to the startle circuits. Tetanic stimulation of either MGN or AAC in vitro or in vivo can induce long‐term potentiation in LA. In the present study, behavioural consequences of tetanization of these auditory afferents were investigated in awake rats. The acoustic startle reflex of rats was enhanced by tetanic stimulation of MGN, but suppressed by that of AAC. All the tetanization‐induced changes of startle diminished within 24 h. Blockade of GABAB receptors in the LA area reversed the suppressive effect of tetanic stimulation of AAC on startle but did not change the enhancing effect of tetanic stimulation of MGN. Moreover, transient electrical stimulation of MGN enhanced the acoustic startle reflex when it lagged behind acoustic stimulation, but inhibited the acoustic startle reflex when it preceded acoustic stimulation. The results of the present study indicate that MGN and AAC afferents to LA play different roles in emotional modulation of startle, and AAC afferents are more influenced by inhibitory GABAB transmission in LA.
Finance and the Business Cycle: International, Inter‐Industry Evidence
Authors: BRAUN MATÍAS , LARRAIN BORJA 
Published: May 2005

ABSTRACTBy considering yearly production growth rates for several manufacturing industries in more than 100 countries during (roughly) the last 40 years, we show that industries that are more dependent on external finance are hit harder during recessions. The observed difference in the behavior of industries is larger when financial frictions are thought to be more prevalent, linking the result directly to the financial mechanism hypothesis. In particular, more dependent industries are more strongly affected in recessions when they are located in countries with poor financial contractibility, and when their assets are softer or less protective of financiers.
Institutional Holdings and Payout Policy
Authors: GRINSTEIN YANIV , MICHAELY RONI 
Published: May 2005

ABSTRACTWe examine the relation between institutional holdings and payout policy in U.S. public firms. We find that payout policy affects institutional holdings. Institutions avoid firms that do not pay dividends. However, among dividend‐paying firms they prefer firms that pay fewer dividends. Our evidence indicates that institutions prefer firms that repurchase shares, and regular repurchasers over nonregular repurchasers. Higher institutional holdings or a concentration of holdings do not cause firms to increase their dividends, their repurchases, or their total payout. Our results do not support models that predict that high dividends attract institutional clientele, or models that predict that institutions cause firms to increase payout.
Are Firms Underleveraged? An Examination of the Effect of Leverage on Default Probabilities
Authors: MOLINA CARLOS A. 
Published: May 2005

ABSTRACTA commonly held view in corporate finance is that firms are less leveraged than they should be, given the potentially large tax benefits of debt. In this paper, I study the effect of firms' leverage on default probabilities as represented by the firms' ratings. Using an instrumental variable approach, I find that the leverage's effect on ratings is three times stronger than it is if the endogeneity of leverage is ignored. This stronger effect results in a higher impact of leverage on the ex ante costs of financial distress, which can offset the current estimates of the tax benefits of debt.
A Comparison of Centralized and Fragmented Markets with Costly Search
Authors: YIN XIANGKANG 
Published: May 2005

ABSTRACTHow does quotation transparency affect financial market performance? Biais's irrelevance proposition in 1993 shows that centralized markets yield the same expected bid–ask spreads as fragmented markets, other things equal. However, de Frutos and Manzano demonstrated in 2002 that expected spreads in fragmented markets are smaller and market participants prefer to trade in fragmented markets. This paper introduces liquidity traders' costs of searching for a better quote into the Biais model and derives opposite conclusions to these previous studies: expected spreads in centralized markets are smaller and liquidity traders prefer centralized markets, while market makers prefer fragmented markets.
New Simplified Technique for 3D Mapping and Ablation of Right Ventricular Outflow Tract Tachycardia
Authors: SALEEM MOEEN A. , BURKETT SCOTT , PASSMAN ROD , DIBS SAMER , ENGELSTEIN ERICA D. , KADISH ALAN H. , GOLDBERGER JEFFREY J. 
Published: May 2005

Objective: To evaluate the safety and efficacy of using a circular multielectrode catheter for mapping and ablation of ventricular tachycardia (VT) or premature ventricular complexes (PVCs) from the right ventricular outflow tract (RVOT).
Background: Three‐dimensional (3D) mapping systems are commonly used for mapping and ablation of RVOT VT and PVCs. Newer catheters that are circular with multiple electrodes, such as the Lasso catheter, are capable of simultaneously recording from multiple points within a circumferential plane. Given the tubular structure of the RVOT, these catheters could be used for mapping tachycardias from the RVOT.
Methods: A retrospective cohort study of patients undergoing radiofrequency (RF) ablation of RVOT VT or PVCs was performed. In group 1 (n = 7), mapping was performed with a single ablation catheter and fluoroscopy. In group 2 (n = 10), 3D mapping using ESI (n = 9) or CARTO (n = 1) was performed. In group 3 (n = 12), mapping was performed with a circular multielectrode catheter (n = 12). All ablations were performed with 4‐mm tip catheters using RF energy.
Results: Catheter ablation for RVOT VT (n = 15) or PVCs (n = 14) was performed on 29 cases in 26 patients, 9 males. Mean age was 35.9 years. In groups 1, 2, and 3, the mean number of lesions was 17.7 ± 7.7, 13.6 ± 7.7, and 18.2 ± 22.7 and the median number of lesions was 20, 13, and 5, respectively. There were no significant differences in the number of lesions, RF time, fluoroscopy time, procedure time, and acute success rate among the three techniques. There were three complications in group 2 and one in group 3.
Conclusion: The use of a circular multielectrode catheter is as effective as the other standard available 3D mapping techniques, both in terms of procedural success and procedural characteristics. Additionally, because of the lower cost associated with using the circular multielectrode catheter approach, further evaluation should be performed to determine whether this is the most cost‐effective approach to 3D mapping and ablation of RVOT tachycardias.
Mechanism of Atrial Flutter Occurring Late After Orthotopic Heart Transplantation with Atrio‐atrial Anastomosis
Authors: MARINE JOSEPH E. , SCHUGER CLAUDIO D. , BOGUN FRANK , KALAHASTY GAUTHAM , ARNALDO FABIAN , CZERSKA BARBARA , KRISHNAN SUBRAMANIAM C. 
Published: May 2005

Objective: We sought to better define the electrophysiologic mechanism of atrial flutter in patients after heart transplantation.
Background: Atrial flutter is a recognized problem in the postcardiac transplant population. The electrophysiologic basis of atrial flutter in this patient population is not completely understood.
Methods: Six patients with cardiac allografts and symptoms related to recurrent atrial flutter underwent diagnostic electrophysiologic study with electroanatomic mapping and radiofrequency catheter ablation. Comparison was made with a control nontransplant population of 11 patients with typical counterclockwise right atrial flutter.
Results: In each case, mapping showed typical counterclockwise activation of the donor‐derived portion of the right atrium, with concealed entrainment shown upon pacing in the cavotricuspid isthmus (CTI). The anastomotic suture line of the atrio‐atrial anastomosis formed the posterior barrier of the reentrant circuit. Ablation of the electrically active, donor‐derived portion of the CTI was sufficient to terminate atrial flutter and render it noninducible. Comparison with the control population showed that the electrically active portion of the CTI was significantly shorter in patients with transplant‐associated flutter and that ablation was accomplished with the same or fewer radiofrequency lesions.
Conclusions: Atrial flutter in cardiac transplant recipients is a form of typical counterclockwise, isthmus‐dependent flutter in which the atrio‐atrial anastomotic suture line forms the posterior barrier of the reentrant circuit. Ablation in the donor‐derived portion of the CTI is sufficient to create bidirectional conduction block and eliminate this arrhythmia. Ablation or surgical division of the donor CTI at the time of transplantation could prevent this arrhythmia.
Dynamic Modeling and Simulation of Satellite Tethered Systems
Authors: Mankala Kalyan K. , Agrawal Sunil K. 
Published: May 2005

Abstract
The objective of this paper is to study the dynamic simulation of a tether as it is deployed or retrieved by a winch on a satellite orbiting around earth. In an effort to understand the problem incrementally, the following three models were developed: (a) Model 1: A tether with constant length moves on earth in the plane of constant gravity; (b) Model 2: A tether is deployed from a drum on earth in the plane of constant gravity, i.e., length of the cable changes during deployment; (c) Model 3: A tether is deployed from a drum on an orbiting satellite. These models have been chosen to bring different aspects as well as levels of difficulty in the analysis. For example, in Model 1, the length of cable is fixed and the gravity direction is constant during motion. The equations of motion for this model are derived using Newton’s laws and Hamilton’s principle to show the equivalence of the two methods. In Model 2, free length of the cable changes during deployment. The changing length of the cable introduces coupled nonlinearities into the motion. Model 3 includes the orbital effect on the motion of deployed cable. Each of these three dynamic models characterized by partial differential equations are first converted to a finite number of ordinary differential equations using Ritz’s procedure and are then numerically integrated using Matlab ODE solvers.
Substrate Specificity and Colorimetric Assay for Recombinant TrzN Derived from
Arthrobacter aurescens
TC1
Authors: Shapir Nir , Rosendahl Charlotte , Johnson Gilbert , Andreina Marco , Sadowsky Michael J. , Wackett Lawrence P. 
Published: May 2005

ABSTRACT

The TrzN protein, which is involved in
s
-triazine herbicide catabolism by
Arthrobacter aurescens
TC1, was cloned and expressed in
Escherichia coli
as a His-tagged protein. The recombinant protein was purified via nickel column chromatography. The purified TrzN protein was tested with 31
s
-triazine and pyrimidine ring compounds; 22 of the tested compounds were substrates. TrzN showed high activity with sulfur-substituted
s
-triazines and the highest activity with ametryn sulfoxide. Hydrolysis of ametryn sulfoxide by TrzN, both in vitro and in vivo, yielded a product(s) that reacted with 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) to generate a diagnostic blue product. Atrazine chlorohydrolase, AtzA, did not hydrolyze ametryn sulfoxide, and no color was formed by amending those enzyme incubations with NBD-Cl. TrzN and AtzA could also be distinguished by reaction with ametryn. TrzN, but not AtzA, hydrolyzed ametryn to methylmercaptan. Methylmercaptan reacted with NBD-Cl to produce a diagnostic yellow product having an absorption maximum at 420 nm. The yellow color with ametryn was shown to selectively demonstrate the presence of TrzN, but not AtzA or other enzymes, in whole microbial cells. The present study was the first to purify an active TrzN protein in recombinant form and develop a colorimetric test for determining TrzN activity, and it significantly extends the known substrate range for TrzN.
Induction of Oxidative Stress by High Hydrostatic Pressure in
Escherichia coli
Authors: Aertsen Abram , De Spiegeleer Philipp , Vanoirbeek Kristof , Lavilla Maria , Michiels Chris W. 
Published: May 2005

ABSTRACT

Using leaderless alkaline phosphatase as a probe, it was demonstrated that pressure treatment induces endogenous intracellular oxidative stress in
Escherichia coli
MG1655. In stationary-phase cells, this oxidative stress increased with the applied pressure at least up to 400 MPa, which is well beyond the pressure at which the cells started to become inactivated (200 MPa). In exponential-phase cells, in contrast, oxidative stress increased with pressure treatment up to 150 MPa and then decreased again, together with the cell counts. Anaerobic incubation after pressure treatment significantly supported the recovery of MG1655, while mutants with increased intrinsic sensitivity toward oxidative stress (
katE
,
katF
,
oxyR
,
sodAB
, and
soxS
) were found to be more pressure sensitive than wild-type MG1655. Furthermore, mild pressure treatment strongly sensitized
E. coli
toward
t-
butylhydroperoxide and the superoxide generator plumbagin. Finally, previously described pressure-resistant mutants of
E. coli
MG1655 displayed enhanced resistance toward plumbagin. In one of these mutants, the induction of endogenous oxidative stress upon high hydrostatic pressure treatment was also investigated and found to be much lower than in MG1655. These results suggest that, at least under some conditions, the inactivation of
E. coli
by high hydrostatic pressure treatment is the consequence of a suicide mechanism involving the induction of an endogenous oxidative burst.
Identification of Unique Type II Polyketide Synthase Genes in Soil
Authors: Wawrik Boris , Kerkhof Lee , Zylstra Gerben J. , Kukor Jerome J. 
Published: May 2005

ABSTRACT

Many bacteria, particularly actinomycetes, are known to produce secondary metabolites synthesized by polyketide synthases (PKS). Bacterial polyketides are a particularly rich source of bioactive molecules, many of which are of potential pharmaceutical relevance. To directly access PKS gene diversity from soil, we developed degenerate PCR primers for actinomycete type II KS
α
(ketosynthase) genes. Twenty-one soil samples were collected from diverse sources in New Jersey, and their bacterial communities were compared by terminal restriction fragment length polymorphism (TRFLP) analysis of PCR products generated using bacterial 16S rRNA gene primers (27F and 1525R) as well as an actinomycete-specific forward primer. The distribution of actinomycetes was highly variable but correlated with the overall bacterial species composition as determined by TRFLP. Two samples were identified to contain a particularly rich and unique actinomycete community based on their TRFLP patterns. The same samples also contained the greatest diversity of KS
α
genes as determined by TRFLP analysis of KS
α
PCR products. KS
α
PCR products from these and three additional samples with interesting TRFLP pattern were cloned, and seven novel clades of KS
α
genes were identified. Greatest sequence diversity was observed in a sample containing a moderate number of peaks in its KS
α
TRFLP. The nucleotide sequences were between 74 and 81% identical to known sequences in GenBank. One cluster of sequences was most similar to the KS
α
involved in ardacin (glycopeptide antibiotic) production by
Kibdelosporangium aridum
. The remaining sequences showed greatest similarity to the KS
α
genes in pathways producing the angucycline-derived antibiotics simocyclinone, pradimicin, and jasomycin.
Balamuthia mandrillaris
, Free-Living Ameba and Opportunistic Agent of Encephalitis, Is a Potential Host for
Legionella pneumophila
Bacteria
Authors: Shadrach Winlet Sheba , Rydzewski Kerstin , Laube Ulrike , Holland Gudrun , Özel Muhsin , Kiderlen Albrecht F. , Flieger Antje 
Published: May 2005

ABSTRACT

Balamuthia mandrillaris
is a free-living ameba and an opportunistic agent of granulomatous encephalitis in humans and other mammalian species. Other free-living amebas, such as
Acanthamoeba
and
Hartmannella
, can provide a niche for intracellular survival of bacteria, including the causative agent of Legionnaires' disease,
Legionella pneumophila.
Infection of amebas by
L. pneumophila
enhances the bacterial infectivity for mammalian cells and lung tissues. Likewise, the pathogenicity of amebas may be enhanced when they host bacteria. So far, the colonization of
B. mandrillaris
by bacteria has not been convincingly shown. In this study, we investigated whether this ameba could host
L. pneumophila
bacteria. Our experiments showed that
L. pneumophila
could initiate uptake by
B. mandrillaris
and could replicate within the ameba about 4 to 5 log cycles from 24 to 72 h after infection. On the other hand, a
dotA
mutant, known to be unable to propagate in
Acanthamoeba castellanii
, also did not replicate within
B. mandrillaris
. Approaching completion of the intracellular cycle,
L. pneumophila
wild-type bacteria were able to destroy their ameboid hosts. Observations by light microscopy paralleled our quantitative data and revealed the rounding, collapse, clumping, and complete destruction of the infected amebas. Electron microscopic studies unveiled the replication of the bacteria in a compartment surrounded by a structure resembling rough endoplasmic reticulum. The course of intracellular infection, the degree of bacterial multiplication, and the ultrastructural features of a
L. pneumophila
-infected
B. mandrillaris
ameba resembled those described for other amebas hosting
Legionella
bacteria. We hence speculate that
B. mandrillaris
might serve as a host for bacteria in its natural environment.