bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local activation of protein kinase A inhibits morphogenetic movements during Xenopus gastrulation
Authors: Song Byung‐Ho , Choi Sun‐Cheol , Han Jin‐Kwan 
Published: April 2003

AbstractcAMP‐dependent protein kinase (PKA) has various biological roles in many organisms. However, little is known about its role in the developmental processes of vertebrates. In this study, we describe the functional analysis of PKA during gastrulation movements in Xenopus laevis. Overexpression of constitutively active PKA (cPKA) in the dorsal equatorial region of the embryo affects morphogenetic movement during gastrulation. We also show that intrinsic differences of PKA activities along the dorsoventral axis are set up and the level of PKA activity on the dorsal region is lower than that on the ventral region from late blastula to gastrula stages. In addition, PKA activation in animal explants inhibits activin‐induced elongation. In cPKA‐injected embryos, there were no changes in the expressions of markers involved in mesoderm specification, although the correct expression domains of these genes were altered. The effects of PKA activation can be restored by coexpression of PKI, a pseudosubstrate of PKA. We further analyzed the effects of PKA activation on the behavior of migratory gastrulating cells in vitro. Expression of cPKA in head mesoderm cells causes less polarized and/or randomized migration as demonstrated by a directional cell migration assay. Finally, we show that RhoA GTPase lies downstream of PKA, affecting activin‐induced convergent extension movements. Taken together, these results suggest that overexpressed PKA can modulate a pathway responsible for morphogenetic movements during Xenopus gastrulation. Developmental Dynamics 227:91–103, 2003. © 2003 Wiley‐Liss, Inc.
Revisiting the empirical estimation of the effect of margin changes on futures trading volume
Authors: Dutt Hans R. , Wein Ira L. 
Published: April 2003

AbstractThis study revisits the empirical estimation of the effect of margin requirements on trading volume. Although
theory suggests that margin requirements impose a cost to traders and will therefore likely reduce volume traded,
empirical examinations have generally failed to find this association. The contention of this article is that the
theory is correct, but empirical estimation has generally neglected to adjust margins for underlying price risk.
After adjusting for risk, this analysis finds economically and statistically significant negative effects of
margin requirements on trading volume as predicted by theory. This study examined 6 contracts over a
17‐year time period and found that financial futures contracts (gold, Dow Jones, and 10‐Year
Treasury Notes) were considerably more sensitive to changes in margin requirements than agricultural futures
(wheat, corn, and oats). © 2003 Wiley Periodicals, Inc. Jrl Fut Mark 23:561–576, 2003
The effectiveness of coordinating price limits across futures and spot markets
Authors: Chou Pin‐Huang , Lin Mei‐Chen , Yu Min‐Teh 
Published: April 2003

AbstractWe extend the work of Brennan (1986) to investigate whether the imposition
of spot price limits can further reduce the default risk and lower the effective margin requirement for a futures
contract that is already under price limits. Our results show that spot price limits do indeed further reduce the
default risk and margin requirement effectively. In addition, the more precise the information is that comes from
the spot market, the more the spot price limit rule constrains the information available to the losing party. The
default probability, contract costs, and margin requirements are then lowered to a greater degree. Furthermore,
for a given margin, both spot price limits and futures price limits can partially substitute for each other in
ensuring contract performance. The common practice of imposing equal price limits on both the spot and futures
markets, though not coinciding with the efficient contract design, has a lower contract cost and margin
requirement than that without imposing spot price limits. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark
23:577–602, 2003
The valuation of multiple stock warrants
Authors: Lim Kian‐Guan , Terry Eric 
Published: April 2003

AbstractThe issue of multiple series of stock purchase warrants by the same firm is an interesting financial structure
not just in America, but is common in countries such as Switzerland, Malaysia, and Singapore. This paper derives
valuation formulas for multiple series of outstanding warrants. The theoretical warrant prices from this model are
compared against existing models. We report a subtle slippage effect and also a cross dilution effect that cause
the existing models, such as Galai‐Schneller model, to be inappropriate for pricing such classes of multiple
warrants. We also provide an example to illustrate the practicality of our model. The Greeks of the model are also
derived in this paper. The complexity of multiple warrants could extend to other classes of contingent securities
issued by the same firm but with differing expiry terms. © 2003 Wiley Periodicals, Inc. Jrl Fut Mark
23:517–534, 2003
Dissociable neural responses in the hippocampus to the retrieval of facial identity and emotion: An event‐related fMRI study
Authors: Iidaka Tetsuya , Terashima Shigeo , Yamashita Koichi , Okada Tomohisa , Sadato Norihiro , Yonekura Yoshiharu 
Published: April 2003

AbstractIn studies with brain‐damaged patients and experimental animals, the medial temporal lobe, including the hippocampus and parahippocampal gyrus, has been found to play a critical role in establishing declarative or episodic memory. We measured the neural response in these structures, using event‐related functional magnetic resonance imaging, while six healthy subjects performed the retrieval task for facial identity and emotion, respectively. Under the identity condition, the subjects participated in a yes/no recognition test for neutral faces learned before the scanning. Under the emotion condition, the subjects learned the faces with positive or negative expression and retrieved their expressions from neutral cue faces. The results showed that the left hippocampus is primarily involved in the identification of learned faces, and that the adjacent parahippocampal gyrus responds more to target than to distracter events. These results indicate a specific engagement of the left hippocampal regions in conscious recollection and identification of physiognomic facial features. The activity in the right hippocampus increased under both the identity and emotion conditions. The present results may relate with the functional model of face recognition in which the left hemisphere contributes to the processing of detailed features and the right hemisphere is efficient in the processing of global features. Hippocampus 2003;13:429–436. © 2003 Wiley‐Liss, Inc.
Reversible inactivation of the hippocampal formation in food‐storing black‐capped chickadees (Poecile atricapillus)
Authors: Shiflett Michael W. , Smulders Tom V. , Benedict Lauryn , DeVoogd Timothy J. 
Published: April 2003

AbstractThe role of the hippocampal formation (HF) in memory processing was assessed in food‐storing black‐capped chickadees (Poecile atricapilla) by reversibly inactivating the HF during different memory tests. The memory tests required birds to remember a location based on spatial cues only, or based on a combination of both spatial and distinct visual cues. Inactivation of the HF impaired short‐term spatial memory, but not visual‐spatial memory. Inactivation of the HF impaired the retrieval of short‐term (15 min) spatial memories, but not long‐term (3‐h) spatial memories. The pattern of deficits produced by inactivation of the HF in chickadees suggests a possible function of the hippocampal specialization of food‐storing birds, as well as extends the notion of functional homology between the avian and mammalian HF. Hippocampus 2003;13:437–444. © 2003 Wiley‐Liss, Inc.
Density of μ‐opioid receptors in the hippocampus of adult male and female rats is altered by prenatal morphine exposure and gonadal hormone treatment
Authors: Šlamberová Romana , Rimanóczy Ágnes , Bar Noffar , Schindler Cheryl J. , Vathy Ilona 
Published: April 2003

AbstractThe present in vitro autoradiography study demonstrates that prenatal exposure to morphine alters the density of μ‐opioid receptors in the hippocampus of adult female but not adult male rats. Prenatal morphine exposure increased the μ‐opioid receptor density in the CA1 of ovariectomized (OVX) females and in the CA3 of OVX, estradiol benzoate‐plus progesterone (EB+P)‐treated females, but decreased it in CA3 of OVX females. There were also hormonal effects on μ‐opioid receptor density in adult female rats. In the CA1, only morphine‐exposed but not saline‐exposed, hormone‐treated females (EB, P, or EB+P) had a decrease in μ‐opioid receptor density relative to OVX females. Both saline‐exposed and morphine‐exposed, OVX females after gonadal hormone replacement had a lower density of μ‐opioid receptors in the CA3 and in the dentate gyrus (DG) than OVX females. In male rats, there was a decrease in μ‐opioid receptor density in the CA1 and CA3 of gonadectomized (GNX), testosterone 17β‐proprionate (TP)‐treated males relative to GNX males regardless of prenatal morphine exposure. In the DG, the μ‐opioid receptor density was reduced only in morphine‐exposed but not in saline‐exposed, TP‐treated males compared with GNX males. Thus, our data demonstrate that μ‐opioid receptor density in the hippocampus is affected by prenatal morphine exposure and by male and female gonadal hormones. Hippocampus 2003;13:461–471. © 2003 Wiley‐Liss, Inc.
Opioid peptide release in the rat hippocampus after kainic acid‐induced status epilepticus
Authors: Rocha L. , Maidment N.T. 
Published: April 2003

AbstractIt has been suggested that kainic acid enhances opioid peptide release. However, no direct evidence exists to support this hypothesis. The main aim of the present study was to determine whether such release occurs in the hippocampus of the rat after status epilepticus induced by kainic acid. Microdialysis experiments revealed significant opioid peptide release in the hippocampus 90–150 min (100%) and 270–300 min (50%) after kainic acid‐induced status epilepticus. The peptides released were identified by high‐performance liquid chromatography linked to radioimmunoassay as Met‐enkephalin, Leu‐enkephalin, Dynorphin‐A (1–6), and Dynorphin‐A (1–8). Reduced extracellular opioid peptide immunoreactivity was detected 28 days after status epilepticus (38% compared with control situation). The present results indicate an important activation of opioid peptide systems by kainic acid‐induced status epilepticus. In addition, the reduced hippocampal extracellular opioid peptide levels long‐term after kainic acid administration could have important implications for the progressive nature of epileptogenesis. Hippocampus 2003;13:472–480. © 2003 Wiley‐Liss, Inc.
Temporal firing characteristics and the strategic role of subicular neurons in short‐term memory
Authors: Hampson Robert E. , Deadwyler Sam A. 
Published: April 2003

AbstractThe role of subicular neurons is explored with respect to their participation in short‐term memory during performance of a spatial Delayed‐Nonmatch‐to‐Sample (DNMS) task by well‐trained rats. Subicular and CA1 neuron firing was examined in the same animals in relation to the encoding of task‐relevant events during the DNMS trial. The results indicate that subicular neurons have completely different firing signatures than well‐characterized hippocampal neurons in this task. Firing patterns of subicular neurons consisted of five different categories spanning all three phases of the DNMS trial, but concentrated mostly within the Sample and early portion of the Delay period. Unlike hippocampal neurons, subicular cells did not exhibit conjunctive firing correlates with respect to particular combinations of task events; rather, subicular cell firing was differentiated primarily on the basis of temporal specificity within the trial. Only two of the five subicular cell types fired differentially on correct versus error trials; however, one cell type exhibited such differential firing as an inverse function of duration of delay interval. Experiments employing γ‐aminobutyric acid GABAB receptor agonists and antagonists showed that both behavioral performance as well as subicular cell firing were disrupted significantly by baclofen at short delays, while performance at long delays and hippocampal cell firing were relatively immune to this effect. The relevance of subicular cell firing in the task with respect to its temporal relation to delay‐dependent hippocampal neuronal activity suggests that the structures have complementary roles in the encoding and representation of items in short‐term memory. Hippocampus 2003;13:529–541. © 2003 Wiley‐Liss, Inc.
Mitochondrial distribution and glycogen dynamics suggest diffusion constraints in muscle fibers of the blue crab, Callinectes sapidus
Authors: Boyle Kim‐Laura , Dillaman Richard M. , Kinsey Stephen T. 
Published: April 2003

AbstractThe scaling of mitochondrial distribution, citrate synthase activity, and post‐contractile glycogen recovery was examined in muscle fibers of the blue crab, Callinectes sapidus. The fast‐twitch muscle fibers of C. sapidus can reach extremely large dimensions, which may impose constraints on aerobic metabolic processes. However, muscle cells from small crabs are not giant, meaning that during development muscle fibers cross and greatly exceed the surface area to volume (SAV) and diffusion threshold that is adhered to by the cells of most organisms. Cell diameters in the smallest size class were ≃100 µm, while the largest size class had cell diameters in excess of 500 µm. In the smallest cells, the fractional area of subsarcolemmal and intermyofibrillar mitochondria was similar. However, in the largest cells, mitochondria were almost exclusively subsarcolemmal. Total fractional area of mitochondria was highest in the largest cells due to a proliferation of subsarcolemmal mitochondria. In contrast, citrate synthase activity decreased as cell size increased. Following burst contractile activity, glycogen concentrations decreased significantly and remained depressed for several hours in muscle comprised of giant cells, consistent with previous findings that anaerobic glycogenolysis fuels certain components of post‐contractile recovery. However, in muscle composed of the smallest muscle cells, glycogen levels did not decrease significantly following burst activity. While normal scaling of aerobic metabolism would predict a slower aerobic recovery in larger animals, the present results suggest that cellular organization, SAV, and intracellular diffusion distances also impose constraints on aerobic processes in C. sapidus. J. Exp. Zool. 297A:1–16, 2003. © 2003 Wiley‐Liss, Inc.
Melatonin and locomotor activity in the fiddler crab Uca pugilator
Authors: Tilden Andrea R. , Shanahan J. Kearney , Khilji Zahra S. , Owen Jeffrey G. , Sterio Thomas W. , Thurston Kristy T. 
Published: April 2003

AbstractThe influence of melatonin on locomotor activity levels was measured in the fiddler crab Uca pugilator. First, activity in untreated, laboratory‐acclimated crabs was measured over 48 hours in a 12L:12D photoperiod; this study showed a nocturnal increase in activity. In eyestalk‐ablated crabs, overall activity was significantly reduced, and no significant activity pattern occurred. Next, crabs were injected with melatonin or saline (controls) at various times during the 12L:12D photoperiod (0900h, 1200h, and twice at 2100h; each trial was separated by 3–4 days) and monitored for 3 hr post‐injection. Control crabs had low activity during early photophase, high at mid‐photophase, increasing activity during the first scotophase trial, and decreasing activity during the second scotophase trial. Melatonin had no significant influence on activity when injected during the early‐photophase activity trough or early‐scotophase activity decline, but significantly increased activity when injected during the mid‐photophase activity peak and early‐scotophase activity incline. Next, crabs were injected during an early scotophase activity trough and monitored throughout the twelve‐hour scotophase. Melatonin did not increase activity until the mid‐scotophase activity increase, approximately 6 hours later, showing that the pharmacological dosage persisted in the crabs' systems and had later effects during the incline and peak of activity but not the trough. Eyestalk‐ablated crabs were injected with melatonin or saline during early photo‐ and scotophase. Melatonin significantly increased activity in the photophase but not the scotophase trial, indicating that the responsiveness to melatonin continues following eyestalk removal, but the timing may not match that of intact crabs. Melatonin may be involved in the transmission of environmental timing information from the eyestalks to locomotor centers in U. pugilator. J. Exp. Zool. 297A:80–87, 2003. © 2003 Wiley‐Liss, Inc.
Synthesis of 14C‐labelled myosmine, [2′‐14C] ‐3‐(1‐pyrrolin‐2‐yl)pyridine
Authors: Tyroller Stefan , Zwickenpflug Wolfgang , Richter Elmar 
Published: April 2003

Abstract14C‐Labelled myosmine ([2′‐14C]‐3‐(1‐pyrrolin‐2‐yl)pyridine) was synthesized for autoradiography studies starting from [carboxyl‐14C]‐nicotinic acid by initial esterification of the latter in the presence of 1,1,1‐triethoxyethane. Without any purification the ethyl nicotinate formed was directly reacted with N‐vinyl‐2‐pyrrolidinone in the presence of sodium hydride, yielding 14C‐labelled myosmine. The product was purified by silica gel column chromatography. The radiochemical yield was 15% and the specific activity 55.2 mCi/mmol. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and radiolabelling of [123I]‐4‐iodo‐N‐(4‐(4‐(2‐methoxyphenyl)‐piperazin‐1‐yl)butyl)‐benzamide, a potential dopamine D3 antagonist for SPECT studies
Authors: Staelens L. , Dumont F. , De Vos F. , Oltenfreiter R. , Vandecapelle M. , Dierckx R. A. , Slegers G. 
Published: April 2003

AbstractSchizophrenia is a devastating mental disorder characterized by relapsing psychotic episodes accompanied with emotional, professional and social decline. The classical dopamine hypothesis of schizophrenia postulates that hyperactivity of dopaminergic neurotransmission is responsible for the positive symptoms of the disorder. More exactly hyperactivity of the dopamine D3 receptor system is thought to be involved in the pathology of schizophrenia. Therefore, a new 123I‐labelled compound was developed which may allow in vivo visualization of the D3 receptor by SPECT. [123I]‐4‐iodo‐N‐(4‐(4‐(2‐methoxyphenyl)‐piperazin‐1‐yl)butyl)‐benzamide was synthesized and labelled by electrophilic aromatic substitution of the tributylstannyl derrivative. The radiochemical yield was 82–85% and the specific activity was >2.96 Ci/µmol. Copyright © 2003 John Wiley & Sons, Ltd.
Syntheses of 5‐(2‐radiohaloethyl)‐ and 5‐(2‐radiohalovinyl)‐2′‐ deoxyuridines. Novel types of radiotracer for monitoring cancer gene therapy with PET
Authors: Yu Chung‐Shan , Eisenbarth Joseph , Runz Armin , Weber Klaus , Zeisler Stephan , Oberdorfer Franz 
Published: April 2003

AbstractSyntheses of 5‐(2‐[18F]fluoroethyl)‐ (1), 5‐(2‐[80Br]bromoethyl)‐ (2), un‐deprotected (E)‐5‐(2‐[18F]fluorovinyl)‐ (3) and (E)‐5‐(2‐[80Br]bromovinyl)‐2′‐deoxyuridines (4) as the tracers for monitoring cancer gene therapy with positron emission tomography were described. Decay corrected radiochemical yield and synthesis time including labeling and HPLC purification from end of bombardment for 1 was 9.5% and 2 hours, respectively; yield and time for 2 was 16% and 2 hours, respectively. Chemical (approximate to radiochemical) yield and time for synthesis of 3 was 7.5% and 7 minutes, respectively. Radiochemical yield and synthesis time including labeling and HPLC purification of an analytical sample of 4 was 60% and 30 minutes, respectively. Both 2 and 4 received the side reactions during HPLC purification, i.e. ring closure and cleavage of glycosidic bond, respectively. Application of 2 and 4 needed to be confirmed by in vitro or in vivo experiments. Radiochemical yield of 1 could be optimized by employing a modified protocol for preparation of its precursor. The preparation of fluorovinyl counterparts had demonstrated the potential utility of the stannane, 3‐tolyl‐3′,5′‐di‐O‐acetyl‐(E)‐5‐(2‐stannylvinyl)‐2′‐deoxyuridine 7. Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis of [14C]‐l‐tryptophan and [14C]‐5′‐hydroxy‐l‐tryptophan labeled in the carboxyl group
Authors: Boroda E. , Kański R. , Kańska M. 
Published: April 2003

AbstractThe synthesis of selectively 14C‐labeled l‐tryptophan and its derivative 5‐hydroxy‐l‐tryptophan using chemical and multienzymatic methods is reported. The mixture containing [1‐14C[‐dl‐alanine, indole or 5‐hydroxyindole has been converted to [1‐14C]‐l‐tryptophan or 5′‐hydroxy‐[1‐14C]‐l‐tryptophan, respectively, in a one‐pot multienzymatic reaction using four enzymes: d‐amino acid oxidase, catalase, glutamic‐pyruvic transaminase and tryptophanase. Copyright © 2003 John Wiley & Sons, Ltd.
Preparation of [11C]formaldehyde using a silver‐containing ceramic catalyst
Authors: Roeda D. , Dollé F. 
Published: April 2003

AbstractA ceramic material, prepared from kaolin doped with silver ions in various concentrations, was evaluated as a catalyst for the conversion of [11C] methanol into [11C]formaldehyde in a gas flow system. Employment of [11C] methanol with a minimized water content, 300 mg of catalyst (20% of silver) at 500°C and a carrier gas flow rate of 40 mL/min resulted in a radiochemical decay‐corrected [11C]formaldehyde yield of 67% relative to [11C]methanol. Wet [11C]methanol under the same conditions gave 54% of [11C] formaldehyde. Copyright © 2003 John Wiley & Sons, Ltd.
Carbon/Carbon Composite Friction Discs for Aerospace
Authors: Buchgraber W. 
Published: April 2003

AbstractCarbon/carbon friction discs are produced at Newmet Composites (a division of New Metals & Chemicals Ltd.) for flap jam systems in airplanes. They offer excellent mechanical and friction properties. New carbon/carbon composite grades have been developed at Newmet Composites during the last few years. Another material that is used for this applications is bronze. Different material grades and different designs are compared in this paper. The key‐properties discussed are compression strength, flexural strength and friction behaviour. The friction tests were simulating the friction behavior during the application of such discs. Compression tests were made to define the possible application: For the application in the flap jam system the compression strength has to be 207 MPa at the minimum, for other applications this is not necessarily required. A test described briefly in this paper was developed for flexural strength. The flexural strength is not very important during the application, but important when the discs are being handled and built in. It could be shown that both production parameters and design have a significant influence on the performance of carbon/carbon friction discs. These results are needed to define further applications for these materials. Finally the material carbon/carbon is briefly compared with alternative materials.