bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Inhomogeneity of Sympathetic Nerve Function in Hibernating Myocardium
Authors: Luisi Andrew J. , Fallavollita James A. , Suzuki Gen , Canty John M.
Published: October 2002

Background—

Although humans and swine with hibernating myocardium have an increased risk of sudden death, the contribution of chronic alterations in sympathetic nerve function is unknown. Acute transmural ischemia causes inhomogeneity in sympathetic innervation that may lead to lethal arrhythmias, but it is unclear whether similar abnormalities develop in response to chronic reversible ischemia.

Methods and Results—

Swine were chronically instrumented with a left anterior descending coronary artery (LAD) stenosis that produced hibernating myocardium after 3 months. Resting subendocardial flow (LAD 0.75±0.14 versus 1.19±0.14 mL · min
−1
· g
−1
,
P
<0.05) and wall thickening (LAD 15±3% versus 40±2%,
P
<0.05) were reduced compared with normal remote regions, without triphenyltetrazolium chloride evidence of necrosis.
131
I-meta-iodobenzylguanidine (MIBG) was used to assess integrity of the norepinephrine uptake-1 mechanism, and the spatial and transmural distributions were quantified by ex vivo counting. In hibernating myocardium, MIBG deposition was decreased in each layer, with the greatest reduction in the subendocardium (LAD subendocardium 0.28±0.02 versus 0.42±0.04 mL · g
−1
· min
−1
in normal,
P
<0.05; LAD subepicardium 0.31±0.03 versus 0.38±0.04 mL · g
−1
· min
−1
in normal,
P
<0.05). In contrast, there were no spatial alterations of MIBG deposition in sham-instrumented animals.

Conclusions—

The sympathetic norepinephrine uptake-1 mechanism is impaired in hibernating myocardium. These findings raise the possibility that chronic alterations in sympathetic innervation contribute to the excess mortality seen in the setting of hibernating myocardium.
Smoking Is Associated With Altered Endothelial-Derived Fibrinolytic and Antithrombotic Factors
Authors: Barua Rajat S. , Ambrose John A. , Saha Dhanonjoy C. , Eales-Reynolds Lesley-Jane
Published: October 2002

Background—

Data about the effects of smoking on thrombo-hemostatic factors (tissue factor [TF] and tissue factor pathway inhibitor [TFPI-1]) are limited and on fibrinolytic factors (tissue plasminogen activator [t-PA] and plasminogen activator inhibitor-1 [PAI-1]) are debatable. The present study investigated the smoking-related, endothelial cell (EC)–specific responses for these factors and their relation to nitric oxide (NO) production in vitro.

Methods and Results—

Serum from 8 nonsmokers and 15 smokers were incubated with confluent (≈85%) human umbilical vein endothelial cells (HUVECs) in 24-well tissue-culture plates for 12 hours. After the incubation, basal NO, t-PA, PAI-1, TF, TFPI-1 production, and substance P (SP)–stimulated NO, t-PA, and PAI-1 production were determined. HUVECs treated with smokers’ serum showed lower basal (
P
<0.02) and SP-stimulated (
P
=0.059) t-PA production but similar basal and stimulated PAI-1 production (
P
=0.9 and
P
=0.6) compared with nonsmokers. Basal t-PA/PAI-1 molar ratio was significantly reduced in smokers (
P
<0.005). TFPI-1 level in the cell culture supernatant was also significantly lower in smokers compared with the nonsmoker group (
P
<0.05) with no difference in TF level between both groups (
P
=0.5). As previously reported, both basal (
P
<0.001) and SP-stimulated (
P
<0.05) NO production were significantly reduced in smokers. Basal TFPI-1 in culture correlated positively with basal NO production (
r
=0.42,
P
=0.04) and negatively with serum cotinine level (
r
=−0.6,
P
=0.01).

Conclusions—

These results indicate that cigarette smoking is associated with alterations in EC-derived fibrinolytic (t-PA) and antithrombotic (TFPI-1) factors. To our knowledge, this is the first demonstration that EC-derived TFPI is affected by smoking and endogenous NO or that the degree of smoke exposure may influence TFPI levels in an EC milieu.
Endogenous Endothelin-1 Limits Exercise-Induced Vasodilation in Hypertensive Humans
Authors: McEniery Carmel M. , Wilkinson Ian B. , Jenkins David G. , Webb David J.
Published: October 2002

Essential hypertension is a common disorder, associated with increased endothelin-1–mediated vasoconstrictor tone at rest. We hypothesized that increased vasoconstrictor activity of endothelin-1 might explain why the normal decrease in peripheral vascular resistance in response to exercise is attenuated in hypertensive patients. Therefore, we investigated the effect of endothelin A (ET
A
) receptor blockade on the vasodilator response to handgrip exercise. Forearm blood flow responses to handgrip exercise (15%, 30%, and 45% of maximum voluntary contraction) were assessed in hypertensive patients and matched normotensive subjects, before and after intra-arterial infusions of the ET
A
receptor antagonist BQ-123; a control dilator, hydralazine; and placebo (saline). Preinfusion (baseline) vasodilation in response to exercise was significantly attenuated at each workload in hypertensive patients compared with normotensive subjects. Intra-arterial infusions of hydralazine and saline did not increase the vasodilator response to exercise in either hypertensives or normotensives at any workload. The vasodilator response to exercise was markedly enhanced after BQ-123 at the 2 higher workloads in hypertensives (157±48%,
P
<0.01; 203±58%,
P
<0.01) but not in normotensives. This suggests that the impaired vasodilator response to exercise in hypertensive patients is, at least in part, a functional limitation caused by endogenous ET
A
receptor–mediated vasoconstriction. Treatment with endothelin receptor antagonists may, therefore, increase exercise capacity in essential hypertension.
Simvastatin Prevents Angiotensin II–Induced Cardiac Alteration and Oxidative Stress
Authors: Delbosc Sandrine , Cristol Jean-Paul , Descomps Bernard , Mimran Albert , Jover Bernard
Published: October 2002

The influence of the HMG-CoA reductase inhibitor simvastatin was assessed on the cardiovascular alterations and production of free radicals associated with chronic angiotensin II (Ang II) infusion. Simvastatin (60 mg/kg per day PO) or placebo were given concomitantly for 10 days in Sprague-Dawley rats infused with Ang II (200 ng/kg per minute SC, osmotic pump). In addition, simvastatin or placebo was also given in vehicle-infused rats. Tail-cuff pressure and albuminuria were measured before and at the end of the treatment period. Cardiac weight, carotid structure, production of reactive oxygen species (ROS, by chemiluminescence) by polymorphonuclear leukocytes and aortic wall as well as protein and lipid oxidation products were determined at the end of the study. Ang II increased tail-cuff pressure by 56±12 mm Hg and simvastatin blunted the development of hypertension by ≈70% (19±5 mm Hg). Increases in heart weight index and carotid cross-sectional area induced by Ang II were obliterated by simvastatin (3.18±0.09 versus 3.46±0.11 mg/g body wt and 0.125±0.010 versus 0.177±0.010 mm
2
, respectively). The Ang II–induced increases in leukocyte and aortic production of ROS as well as protein and lipid oxidation products were prevented by simvastatin. No effect of simvastatin was detected in non–Ang II–infused rats. These results indicate that simvastatin prevented the development of hypertension and cardiovascular hypertrophy together with inhibition of the induced angiotensin II production of ROS. Therefore, inhibition of HMG CoA reductase by statins may have a beneficial effect on cardiovascular alterations through its antioxidant action in experimental Ang II–dependent hypertension.
Effects of Black Race on Forearm Resistance Vessel Function
Authors: Kahn David F. , Duffy Stephen J. , Tomasian Douglas , Holbrook Monika , Rescorl Lynn , Russell Judson , Gokce Noyan , Loscalzo Joseph , Vita Joseph A.
Published: October 2002

Presentation, response to therapy, and clinical outcome in hypertension differ according to race, and these observations could relate to differences in microvascular function. We examined forearm microvascular function in age-matched black (n=56) and white subjects (n=62) using intra-arterial agonist infusion and venous occlusion plethysmography. In normotensive subjects (n=70; 34 black and 36 white normotensives), methacholine-, sodium nitroprusside-, and verapamil-induced vasodilation was equivalent in black and white subjects. In hypertensive subjects (n=48; 22 black and 26 white hypertensives), the vasodilator response to methacholine was markedly lower in black subjects compared with white subjects (
P
<0.001). The vasodilator responses to sodium nitroprusside and verapamil, however, were equivalent in black and white hypertensive subjects. Acute ascorbic acid infusion improved the methacholine response equally in black and white hypertensive patients, suggesting that a difference in a rapidly reversible form of oxidative stress does not explain these findings. Thus, the present study demonstrates important racial differences in vascular function and a marked impairment in endothelial vasomotor function in black patients with hypertension. Further studies will be required to elucidate the mechanisms and determine whether these insights will lead to more appropriately tailored management of hypertension and its complications.
Upregulation of L-Type Ca
2+
Channels in Mesenteric and Skeletal Arteries of SHR
Authors: Pratt Phillip F. , Bonnet Sebastien , Ludwig Lynda M. , Bonnet Pierre , Rusch Nancy J.
Published: October 2002

An increased Ca
2+
influx attributed to dihydropyridine-sensitive L-type Ca
2+
channels has been demonstrated in mesenteric vascular smooth muscle cells of spontaneously hypertensive rats (SHR). This study examined whether an upregulation of the pore-forming α
1C
subunit of the L-type Ca
2+
channel underlies this ionic defect. With the use of mesenteric arcade arteries from 12- to 16-week-old SHR and normotensive Wistar Kyoto (WKY) rats, reverse transcriptase–polymerase chain reaction demonstrated an increased level of amplified cDNA corresponding to the α
1C
subunit mRNA in the SHR arteries. Western blots confirmed that the increased mRNA expression was associated with a 3.4-fold increase in the immunoreactive signal of the α
1C
subunit protein in SHR compared with WKY mesenteric arteries, and immunocytochemistry confirmed this abnormality at the single-cell level. Finally, isolated mesenteric arteries from SHR were highly reactive to Bay K8644 and developed anomalous Ca
2+
-dependent tone, suggesting a functional role for α
1C
subunit upregulation in vascular hyperreactivity. To determine if these Ca
2+
channel abnormalities extended to the SHR skeletal muscle bed, we repeated a similar series of studies in WKY and SHR hind limb arteries. Skeletal muscle arteries from SHR also expressed higher levels of α
1C
subunit mRNA and protein than WKY arteries and developed anomalous Ca
2+
-dependent tone attributed to L-type Ca
2+
channels. Our data provide the first evidence that the α
1C
subunit mRNA and protein are upregulated in SHR arteries and that the increased numbers of L-type Ca
2+
channel pores are associated with the generation of abnormal vascular tone.
Ouabain-Binding Protein(s) From Human Plasma
Authors: Parhami-Seren Behnaz , Haberly Richard , Margolies Michael N. , Haupert Garner T.
Published: October 2002

Conservation of the binding site on mammalian Na
+
,K
+
-ATPase for cardiac glycosides and the importance of the Na
+
pump in mammalian cellular physiology has stimulated the search for a mammalian analog of these plant compounds. One candidate, isolated from brain and blood, appears to be ouabain itself or a closely related isomer, the ouabain-like compound. Little is known about the circulating form. Because human steroid hormones circulate with carrier proteins, we produced a ouabain-specific monoclonal antibody (mAb 1-10) and used it to probe normal human plasma for ouabain-protein carrier complex. Ouabain-like biological activity was isolated in association with protein bands of 80, 50, and 25 kDa. These proteins appear to be human immunoglobulins or immunoglobulin-like because they are recognized by anti-human immunoglobulin antibodies, but not by anti-mouse immunoglobulin antibodies. The protein-containing fractions inhibit the binding of mAb 1-10 to immobilized ouabain, and with further purification on protein A, the immunoglobulin-like protein binds radioactive ouabain with an IC
50
of 200 to 600 nmol/L, but binds digoxin with 100-fold less affinity, suggesting specificity for ouabain or its isomer. Active protein fractions after purification on C
18
inhibit Na
+
pump activity in human erythrocytes (IC
50≈
4 nmol/L, ouabain equivalents), and this chromatography appears to dissociate the ouabain-like compound from the immunoglobulin protein(s). These immunoglobulin-like molecules may represent a subset of immunoglobulins (≤0.5% of total protein A immunoglobulin) that function as a reservoir and delivery system for ouabain-like compounds in the modulation of human Na
+
, K
+
-ATPase in vivo.
Cyclophilin-Mediated Pathways in the Effect of Cyclosporin A on Endothelial Cells
Authors: Alvarez-Arroyo M. Victoria , Yagüe Susana , Wenger Ronald M. , Pereira Daniel S. , Jiménez Sonsoles , González-Pacheco Francisco R. , Castilla M. Angeles , Deudero Juan José P. , Caramelo Carlos
Published: October 2002

The relative importance of cyclophilin (CyP) versus calcineurin (Cn)-mediated mechanisms in the effect of cyclosporin A (CsA) on endothelial cells (ECs) is largely unknown. In cultured ECs, CsA was cytotoxic/proapoptotic or cytoprotective/antiapoptotic at high or low concentrations, respectively. CsA analogs (MeVal-4-CsA and MeIle-4-CsA), which bind to CyP but do not inhibit Cn, closely reproduced the CsA effects. Based on our previous data, the role of vascular endothelial growth factor (VEGF) as a mediator of CsA-induced cytoprotection was further analyzed. The actions of CsA and CsA analogs were shifted from a protective to a cell-damaging pattern in the presence of a specific anti-VEGF monoclonal antibody (mAb). This positive interaction was further supported by a transient increase in cytosolic free calcium concentration ([Ca
2+
]
i
) by VEGF after pretreatment with either CsA or MeVal-4-CsA and an increase in the expression and synthesis of VEGF receptor 2 (VEGFR2). Of functional importance, blockade of the interaction between VEGF and VEGFR2 by a VEGFR2 mAb abolished the cytoprotective effect of CsA. In addition, preconditioning with low concentrations of CsA or CsA analogs increased both cytoprotection and VEGFR2 mRNA expression when EC were exposed to higher concentrations of CsA. In summary, our results reveal that (1) the biphasic responses to CsA in EC are related to the interaction of CsA with CyP rather than with Cn and (2) VEGF is a critical factor in the cytoprotective effect of CsA, by a mechanism that involves VEGFR2.
Withdrawal of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Inhibitors Elicits Oxidative Stress and Induces Endothelial Dysfunction in Mice
Authors: Vecchione Carmine , Brandes Ralf P.
Published: October 2002

3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) improve endothelial function. We determined whether withdrawal of statin therapy affects endothelium-dependent relaxation in mice and studied the underlying mechanism. Mice were treated with daily injections of cerivastatin (2 mg/kg per day SC), atorvastatin (1 and 10 mg/kg per day SC), or placebo. Vascular reactivity was studied in aortic rings from these mice after 10 days of treatment and after cessation of therapy for several days. Both statins improved endothelium-dependent relaxation to acetylcholine. Compared with control, withdrawal of statin treatment transiently (from day 4 to 7) attenuated endothelium-dependent relaxation. In vessels from animals subjected to atorvastatin withdrawal, the antioxidant tiron restored relaxations. Vascular superoxide anion generation was unaffected by statin therapy but was increased during withdrawal. In mice lacking the gp91phox subunit of the NADPH oxidase, no attenuation of acetylcholine-induced relaxation and no increase in superoxide generation were observed after withdrawal of atorvastatin. In human umbilical vein endothelial cells, statins, which decrease the membrane association of NADPH oxidase–activating Rac-1, increased the activity of this GTPase in whole-cell lysates. Withdrawal of statins induced a translocation of Rac-1 from the cytosol to the membrane and transiently increased NADPH-induced lucigenin chemiluminescence in membrane preparations. Rac-1 inactivation by
Clostridium difficile
toxin B inhibited the cerivastatin-induced oxygen radical production in human umbilical vein endothelial cells. These observations indicate that the withdrawal of statins induces endothelial dysfunction. The underlying mechanism involves activation of a gp91phox-containing NADPH oxidase by Rac-1 and the subsequent scavenging of endothelium-derived NO by superoxide anions generated from this enzyme.
Increased Exchange Current but Normal Ca
2+
Transport via Na
+
-Ca
2+
Exchange During Cardiac Hypertrophy After Myocardial Infarction
Authors: Gómez Ana Maria , Schwaller Beat , Porzig Hartmut , Vassort Guy , Niggli Ernst , Egger Marcel
Published: October 2002

Hypertrophied and failing cardiac myocytes generally show alterations in intracellular Ca
2+
handling associated with changes in the contractile function and arrhythmogenicity. The cardiac Na
+
-Ca
2+
exchange (NCX) is an important mechanism for Ca
2+
extrusion and cell relaxation. Its possible involvement in changes of excitation-contraction coupling (EC-coupling) with disease remains uncertain. We analyzed the NCX function in rat ventricular myocytes 5 to 6 months after experimental myocardial infarction (PMI) produced by left coronary artery ligation and from sham-operated (SO) hearts. Caged Ca
2+
was dialyzed into the cytoplasm via a patch-clamp pipette and Ca
2+
was released by flash photolysis to activate NCX and measure the associated currents (
I
NaCa
), whereas [Ca
2+
]
i
changes were simultaneously recorded with a confocal microscope.
I
NaCa
density normalized to the [Ca
2+
]
i
jumps was 2.6-fold higher in myocytes from PMI rats. The level of total NCX protein expression in PMI myocytes was also increased. Interestingly, although the
I
NaCa
density in PMI cells was larger, PMI and SO myocytes presented virtually identical Ca
2+
transport via the NCX. This discrepancy was explained by a reduced surface/volume ratio (34.8%) observed in PMI cells. We conclude that the increase in NCX density may be a mechanism to maintain the required Ca
2+
extrusion from a larger cell to allow adequate relaxation.
Functionally Novel Tumor Necrosis Factor-α–Modulated CHR-Binding Protein Mediates Cyclin A Transcriptional Repression in Vascular Endothelial Cells
Authors: Kishore Raj , Spyridopoulos Ioakim , Luedemann Corinne , Losordo Douglas W.
Published: October 2002

Local expression of tumor necrosis factor-α (TNF-α) at the sites of arterial injury after balloon angioplasty, suppresses endothelial cell (EC) proliferation and negatively affects reendothelialization of the injured vessel. We have previously reported that in vitro exposure of ECs to TNF-α induced EC growth arrest and apoptosis. These effects were mediated, at least in part, by downregulation of cell cycle regulatory proteins. In the present study, we report potential mechanism(s) for TNF-α–mediated suppression of cyclin A in ECs. TNF-α exposure to ECs completely abrogated cyclin A mRNA expression via mechanisms involving both transcriptional and posttranscriptional modifications. TNF-α inhibited de novo cyclin A mRNA synthesis and suppressed cyclin A promoter activity. Utilizing deletion mutants of human cyclin A promoter, we have identified CDE-CHR (
C
ell cycle–
D
ependent
E
lements–
C
ell cycle genes
H
omology
R
egion) region of cyclin A promoter as a target for TNF-α suppressive action. Experiments to investigate CDE-CHR binding proteins/factors revealed a TNF-α–mediated increase in specific DNA binding activity to the CHR elements. This increase in binding activity by TNF-α was mediated via the induction of a functionally novel 84-kDa protein that binds specifically to CHR in Southwestern assays. UV cross-linking and SDS-PAGE analysis of proteins eluted from specific complex confirmed the presence of this 84-kDa protein. Moreover, induction of this protein by TNF-α was protein synthesis dependent. Additionally, exposure of ECs to TNF-α markedly reduced cyclin A mRNA stability. Targeted disruption of this protein could potentially be a therapeutic strategy to rescue EC proliferation in vivo.
Preoperative Diagnosis of Carotid Artery Stenosis
Authors: Nederkoorn Paul J. , Mali Willem P.Th.M. , Eikelboom Bert C. , Elgersma Otto E.H. , Buskens Erik , Hunink M.G. Myriam , Kappelle L. Jaap , Buijs Pieter C. , Wüst Aloys F.J. , van der Lugt Aad , van der Graaf Yolanda
Published: October 2002

Background and Purpose

—

Carotid endarterectomy has been shown to be beneficial in symptomatic patients with a severe stenosis (70% to 99%) of the internal carotid artery (ICA). Digital subtraction angiography (DSA) is the standard of reference in the diagnosis of carotid artery stenosis but has a relatively high complication rate. In a diagnostic study we investigated the accuracy of noninvasive testing compared with DSA.

Methods

—

In a prospective diagnostic study we performed duplex ultrasound (DUS), magnetic resonance angiography (MRA), and DSA on 350 consecutive symptomatic patients. Stenoses were measured with the observers blinded for clinical information and other test results. Separate and combined test results of DUS and MRA were compared with the reference standard DSA. Only the stenosis measurements of the arteries on the symptomatic side were included in the analyses.

Results

—

DUS analyzed with previously defined criteria resulted in a sensitivity of 87.5% (95% CI, 82.1% to 92.9%) and a specificity of 75.7% (95% CI, 69.3% to 82.2%) in identifying severe ICA stenosis (70% to 99%). Stenosis measurements on MRA yielded a sensitivity of 92.2% (95% CI, 86.2% to 96.2%) and a specificity of 75.7% (95% CI, 68.6% to 82.5%). When we combined MRA and DUS results, agreement between these 2 modalities (84% of patients) gave a sensitivity of 96.3% (95% CI, 90.8% to 99.0%) and a specificity of 80.2% (95% CI, 73.1% to 87.3%) for identifying severe stenosis.

Conclusions

—

MRA showed a slightly better accuracy than DUS in the diagnosis of carotid artery stenosis. To achieve the best accuracy, however, both tests should be performed subsequently.
Rapid Breakdown of Microvascular Barriers and Subsequent Hemorrhagic Transformation After Delayed Recombinant Tissue Plasminogen Activator Treatment in a Rat Embolic Stroke Model
Authors: Dijkhuizen Rick M. , Asahi Minoru , Wu Ona , Rosen Bruce R. , Lo Eng H.
Published: October 2002

Background and Purpose

—

Thrombolytic therapy with recombinant tissue plasminogen activator (rtPA) after stroke increases risk of hemorrhagic transformation, particularly in areas with blood-brain barrier leakage. Our aim was to characterize acute effects of rtPA administration on the integrity of microvascular barriers.

Methods

—

Stroke was induced in spontaneously hypertensive rats by unilateral embolic middle cerebral artery occlusion. Six hours after stroke, rtPA was intravenously administered (n=10). Controls received saline (n=4). Extravasation of the large-diameter contrast agent monocrystalline iron oxide nanocolloid (MION) was assessed with susceptibility contrast-enhanced MRI during rtPA injection. In addition, we performed perfusion MRI and diffusion-weighted MRI. After MRI, 2 hours after rtPA treatment, intracerebral hemorrhage was quantified with a spectrophotometric hemoglobin assay.

Results

—

Late rtPA treatment resulted in increased hemorrhage volume (8.4±1.7 versus 2.9±0.9 μL in controls;
P
<0.05). In MION-injected animals, during rtPA administration, transverse relaxation rate change (ΔR
2
*) increased from 12.4±6.0 to 31.6±19.2 s
−1
(
P
<0.05) in areas with subsequent hemorrhage. Significant ΔR
2
* changes were absent in nonhemorrhagic areas, in animals without injected MION, and in saline-treated animals. Thrombolytic therapy did not improve perfusion in regions with hemorrhagic transformation (cerebral blood flow index was 22.8±19.7% [of contralateral] at 0.5 hours before and 22.4±18.0% at 1 hour after rtPA administration).

Conclusions

—

The ΔR
2
* changes during rtPA delivery in MION-injected animals indicate extravasation of MION, which reflects increased permeability of the blood-brain barrier. This implies that late rtPA treatment rapidly aggravates early ischemia-induced damage to microvascular barriers, thereby enhancing hemorrhagic transformation.
Internet Studios: Teaching Architectural Design On-Line between the United States and Latin America
Authors: Andia Alfredo
Published: October 2002

This article analyzes the pedagogical use of high-end computer graphics and low-and high-bandwidth Internet technology for international architectural education among numerous universities in the Americas. The findings can be applied to any discipline that involves a large number of participants within a design setting. The experiments have allowed design studios from seven schools of architecture in the U.S. and South America to work concurrently in a semesterlong design studio. Most of the collaboration was accomplished by using low-bandwidth Internet communication such as web publishing, chat, computerassisted design software and other technologies such as ISDN broadcasting. The author anticipates future experimentation with high-bandwidth technologies on the Internet2 Abilene Network.
The Split-Brain Human Computer User Interface
Authors: Garvey Gregory P.
Published: October 2002

The author describes his prototype for a split-brain user interface developed for the interactive documentary Anita und Clarence in der Hölle: An Opera for Split-Brains in Modular Parts. Using documentary video from the 1991 Senate Judiciary Committee hearings on the nomination of Clarence Thomas to the U.S. Supreme Court, this interface delivers two independent video and audio streams in parallel to each hemisphere of the brain. Inspired by accounts of split-brain research and anticipated by experiments of the Surrealists, this interface-like work in augmented virtual reality and wearable computing aims at “enhanced” interaction while creating a new aesthetic experience.
Aesthetic Programming: Crafting Personalized Software
Authors: Fishwick Paul A.
Published: October 2002

Marrying traditional methods of computer programming with an artistic temperament allows the birth of a new phenomenon: the aesthetic program. The work of the author and his students builds on visual ap-proaches in programming as well as in software modeling, leading toward a gradual evolution from program to model. The need for the aes-thetic model is increased with the importance of personalized, individually tailored media, as found with web-based style sheets and the economic movement termed “mass customization.” The author and his students have formulated the rube Project methodology around the use of 3D web-based virtual-world model construction. Initial results suggest that these models are artistic, while containing symbolism and concise metaphoric mapping sufficient to be executable on a computer.
Artificial Life and Philosophy
Authors: Moreno Alvaro
Published: October 2002

Artificial Life is developing into a new type of discipline, based on computational construction as its main tool for exploring and producing a science of life “as it could be.” In this area of research, the generation of complex virtual systems, in place of the traditional empirical domain, has become the actual object of theory. This entails a profound change in the tradi-tional relationship between ontological, epistemological and methodological levels of analy-sis, which forces us to recon-sider the differences apparently firmly established between science and philosophy. Even if the frontiers between these two kinds of knowledge do not completely disappear, new, dynamic, complex, technologi-cally mediated interactions are being developed between them.
A Kantian Prescription for Artificial Conscious Experience
Authors: Stuart Susan A.J. , Dobbyn Chris
Published: October 2002

Research in artificial intelli-gence, artificial life and cogni-tive science has not yet provided answers to any of the most perplexing questions about the mind, such as the nature of consciousness or of the self; in this article the authors make a suggestion for a new approach. They begin by setting their project in the broader cognitive science context and argue that little recent research adequately addresses the question of what are the necessary requirements for conscious experience to be possible. Kant addresses this question in his transcendental psychology, and although Kant's work is now over 200 years old the authors believe his approach is worthy of re-examination in the current debate about the mind.
Atoms and Sets: A Characterization of Semantic Number
Authors: Winter Yoad
Published: October 2002

This article analyzes the interactionsof semantic number, morphological number, and quantification. It argues that the traditional typology of distributive and collective predicates is unsuitable for a truth-conditional theory of plurality. A new test is proposed for classifying the semantic number of predicates according to their behavior with singular/plural quantificational noun phrases such as every/all student(s) and no teacher(s). Predicates that are (in)sensitive to such number variations are called atom/set predicates, respectively, and it is shown that this distinction cuts across the traditional distributive/ collective typology. The processes that govern the semantic number of sentences are reanalyzed in these terms.
The Combinatory Morphemic Lexicon
Authors: Bozsahin Cem
Published: October 2002

Grammars that expect words from the lexicon may be at odds with the transparent projection of syntactic and semantic scope relations of smaller units. We propose a morphosyntactic framework based on Combinatory Categorial Grammar that provides flexible constituency, flexible category consistency, and lexical projection of morphosyntactic properties and attachment to grammar in order to establish a morphemic grammar-lexicon. These mechanisms provide enough expressive power in the lexicon to formulate semantically transparent specifications without the necessity to confine structure forming to words and phrases. For instance, bound morphemes as lexical items can have phrasal scope or word scope, independent of their attachment characteristics but consistent with their semantics. The controls can be attuned in the lexicon to language-particular properties. The result is a transparent interface of inflectional morphology, syntax, and semantics. We present a computational system and show the application of the framework to English and Turkish.
Changes in the Spatial Distribution of Visual Attention after Early Deafness
Authors: Proksch Jason , Bavelier Daphne
Published: October 2002

There is much anecdotal suggestion of improved visual skills in congenitally deaf individuals. However, this claim has only been met by mixed results from careful investigations of visual skills in deaf individuals. Psychophysical assessments of visual functions have failed, for the most part, to validate the view of enhanced visual skills after deafness. Only a few studies have shown an advantage for deaf individuals in visual tasks. Interestingly, all of these studies share the requirement that participants process visual information in their peripheral visual field under demanding conditions of attention. This work has led us to propose that congenital auditory deprivation alters the gradient of visual attention from central to peripheral field by enhancing peripheral processing. This hypothesis was tested by adapting a search task from Lavie and colleagues in which the interference from distracting information on the search task provides a measure of attentional resources. These authors have established that during an easy central search for a target, any surplus attention remaining will involuntarily process a peripheral distractor that the subject has been instructed to ignore. Attentional resources can be measured by adjusting the difficulty of the search task to the point at which no surplus resources are available for the distractor. Through modification of this paradigm, central and peripheral attentional resources were compared in deaf and hearing individuals. Deaf individuals possessed greater attentional resources in the periphery but less in the center when compared to hearing individuals. Furthermore, based on results from native hearing signers, it was shown that sign language alone could not be responsible for these changes. We conclude that auditory deprivation from birth leads to compensatory changes within the visual system that enhance attentional processing of the peripheral visual field.
Auditory Cortical Responses to Speech-Like Stimuli in Dyslexic Adults
Authors: Renvall Hanna , Hari Riitta
Published: October 2002

Auditory cortical processing of speech-like sounds was studied in 9 dyslexic and 11 normal-reading adults. Noise/ square-wave sequences, mimicking transitions from a fricative consonant to a vowel, were presented binaurally once every 1.1 sec and the cortical responses were recorded with a whole-scalp neuromagnetometer. The auditory cortices of both hemispheres were less reactive to acoustical changes in dyslexics than in controls, as was evident from the weaker responses to the noise/square-wave transitions. The results demonstrate that dyslexic adults are deficient in processing acoustic changes presented in rapid succession within tens to hundreds of milliseconds. The observed differences could be related to insufficient triggering of automatic auditory attention, resulting, for instance, from a general deficiency of the magnocellular system.
Neural Substrates of Action Event Knowledge
Authors: Kable Joseph W. , Lease-Spellmeyer Jessica , Chatterjee Anjan
Published: October 2002

Human concepts can be roughly divided into entities (prototypically referred to in language by nouns) and events (prototypically referred to in language by verbs). While much work in cognitive neuroscience has investigated how the brain represents different categories of entities, less attention has been given to the more basic distinction between entities and events. We used functional magnetic resonance imaging to examine brain activity while subjects performed a conceptual matching task that required them to access knowledge of objects and actions, using either pictures or words. Since action events involve movement through space, we hypothesized that accessing knowledge of actions would cause greater activation in brain regions involved in motion or spatial processing. In comparison to objects, accessing knowledge of actions through pictures was accompanied by increased activity bilaterally in the human MT/MST and nearby regions of the lateral temporal cortex. Accessing knowledge of actions through words activated areas just anterior and dorsal to area MT/MST on the left, within the posterior aspect of the middle and superior temporal gyri. We propose that the lateral occipital temporal cortex contains a mosaic of neural regions that processes different kinds of motion, ranging from the perception of objects moving in the world to the conception of movement implied in action verbs. The lateral occipital temporal cortex mediates the perceptual and conceptual features of action events, similar to the way that the ventral occipital temporal cortex processes the perceptual and conceptual features of entities.
Preintegration Lateral Inhibition Enhances Unsupervised Learning
Authors: Spratling M. W. , Johnson M. H.
Published: October 2002

A large and influential class of neural network architectures uses postintegration lateral inhibition as a mechanism for competition. We argue that these algorithms are computationally deficient in that they fail to generate, or learn, appropriate perceptual representations under certain circumstances. An alternative neural network architecture is presented here in which nodes compete for the right to receive inputs rather than for the right to generate outputs. This form of competition, implemented through preintegration lateral inhibition, does provide appropriate coding properties and can be used to learn such representations efficiently. Furthermore, this architecture is consistent with both neuroanatomical and neurophysiological data. We thus argue that preintegration lateral inhibition has computational advantages over conventional neural network architectures while remaining equally biologically plausible.
On Optimality in Auditory Information Processing
Authors: Karlsson Mattias F. , Robinson John W. C.
Published: October 2002

We study limits for the detection and estimation of weak sinusoidal signals in the primary part of the mammalian auditory system using a stochastic Fitzhugh-Nagumo model and an action-recovery model for synaptic depression. Our overall model covers the chain from a hair cell to a point just after the synaptic connection with a cell in the cochlear nucleus. The information processing performance of the system is evaluated using so-called φ-divergences from statistics that quantify “dissimilarity” between probability measures and are intimately related to a number of fundamental limits in statistics and information theory (IT). We show that there exists a set of parameters that can optimize several important φ-divergences simultaneously and that this set corresponds to a constant quiescent firing rate (QFR) of the spiral ganglion neuron. The optimal value of the QFR is frequency dependent but is essentially independent of the amplitude of the signal (for small amplitudes). Consequently, optimal processing according to several standard IT criteria can be accomplished for this model if and only if the parameters are “tuned” to values that correspond to one and the same QFR. This offers a new explanation for the QFR and can provide new insight into the role played by several other parameters of the peripheral auditory system.
Training Products of Experts by Minimizing Contrastive Divergence
Authors: Hinton Geoffrey E.
Published: October 2002

It is possible to combine multiple latent-variable models of the same data by multiplying their probability distributions together and then renormalizing. This way of combining individual “expert” models makes it hard to generate samples from the combined model but easy to infer the values of the latent variables of each expert, because the combination rule ensures that the latent variables of different experts are conditionally independent when given the data. A product of experts (PoE) is therefore an interesting candidate for a perceptual system in which rapid inference is vital and generation is unnecessary. Training a PoE by maximizing the likelihood of the data is difficult because it is hard even to approximate the derivatives of the renormalization term in the combination rule. Fortunately, a PoE can be trained using a different objective function called “contrastive divergence” whose derivatives with regard to the parameters can be approximated accurately and efficiently. Examples are presented of contrastive divergence learning using several types of expert on several types of data.
Joint Entropy Maximization in Kernel-Based Topographic Maps
Authors: Hulle Marc M. Van
Published: October 2002

A new learning algorithm for kernel-based topographic map formation is introduced. The kernel parameters are adjusted individually so as to maximize the joint entropy of the kernel outputs. This is done by maximizing the differential entropies of the individual kernel outputs, given that the map's output redundancy, due to the kernel overlap, needs to be minimized. The latter is achieved by minimizing the mutual information between the kernel outputs. As a kernel, the (radial) incomplete gamma distribution is taken since, for a gaussian input density, the differential entropy of the kernel output will be maximal. Since the theoretically optimal joint entropy performance can be derived for the case of nonoverlapping gaussian mixture densities, a new clustering algorithm is suggested that uses this optimum as its “null” distribution. Finally, it is shown that the learning algorithm is similar to one that performs stochastic gradient descent on the Kullback-Leibler divergence for a heteroskedastic gaussian mixture density model.
Crossing Borders, Al-halqa Performance in Morocco from the Open Space to the Theatre Building
Authors: Amine Khalid
Published: October 2002

Around the centrally placed mosque, an Arabo-Islamic city radiates outwards in a series of circles. Al-halqa performance is a free and licensed expressive behavior situated at the medina gates and marketplaces. Some al-halqa-type performances have been transferred to theatre buildings-bringing both new possibilities and difficult contradictions.
“The Wildest Show in the South”: Tourism and Incarceration at Angola
Authors: Adams Jessica
Published: October 2002

Since 1967, prisoners doing hard time at the Louisiana State Penitentiary have volunteered to take part in a rodeo staged for tourists. Few of the inmates have ever ridden a horse before, much less a bucking bronco or bull. Is this spectacle of criminalized bodies per-forming under duress “fun” or public torture?
The Effects of Operator Spatial Perception and Sensory Feedback on Human-Robot Teleoperation Performance
Authors: Lathan Corinna E. , Tracey Michael
Published: October 2002

Teleoperation requires a complex combination of the operator's cognitive, perceptual, and motor skills. Our experiment tested the ability of subjects to teleoperate a remote robot under different conditions of increasing sensory feedback. We also evaluated each operator's spatial perception skills using a battery of tests to understand the effect of spatial perception on the operator's ability to perform the teleoperation task. The experiment showed that the spatial ability of an operator—as reflected by a test battery of two spatial recognition and two spatial manipulation tests—was significantly correlated with the ability to teleoperate the robot through a maze. Surprisingly, providing different combinations of visual, auditory, and vibrotactile feedback to the operator did not significantly change performance. However, there was an interaction between spatial ability and feedback condition that affected teleoperation performance.
Natural Language From Artificial Life
Authors: Kirby Simon
Published: October 2002

This article aims to show that linguistics, in particular the study of the lexico-syntactic aspects of language, provides fertile ground for artificial life modeling. A survey of the models that have been developed over the last decade and a half is presented to demonstrate that ALife techniques have a lot to offer an explanatory theory of language. It is argued that this is because much of the structure of language is determined by the interaction of three complex adaptive systems: learning, culture, and biological evolution. Computational simulation, informed by theoretical linguistics, is an appropriate response to the challenge of explaining real linguistic data in terms of the processes that underpin human language.
Chaebol and Catastrophe: A New View of the Korean Business Groups and Their Role in the Financial Crisis
Authors: Feenstra Robert C. , Hamilton Gary G. , Lim Eun Mie
Published: October 2002

We present a model of industrial organization that has multiple stable equilibria and argue that the high-concentration equilibrium describes Korea's economy and the low-concentration equilibrium describes Taiwan's economy. Past industrial policy of the state may have put Korea's economy in the high-concentration equilibrium, but discontinuation of the policy did not cause the industrial organization to change because this is an economically viable equilibrium.

The high-concentration equilibrium produces a narrower range of final goods than the low-concentration equilibrium, which explains why the 1996 collapse in semiconductor prices caused the less diversified Korean economy to contract more than the more diversified Taiwanese economy. More importantly, this collapse in demand caused Korea's economy to move to a new equilibrium that has a smaller number of business groups, as evidenced by the collapse of the second-tier chaebol and their absorption into the first-tier chaebol. This wave of bankruptcies, combined with the financially precarious state of the merchant banks, created an investor panic that precipitated the crisis, which began with the 17 November 1997 devaluation of the won. This is why economic fundamentals could explain the chaebol bankruptcies before that date and not those after that date. The logic of our model suggests that public policy should focus on reducing the vertical linkages within business groups and not on reducing their horizontal linkages as the current “Big Deal” program of the government is doing.
Total Factor Productivity Growth in East Asia: Implications for the Future
Authors: Kim Jong-il
Published: October 2002

The total factor productivity (TFP) growth controversy and the recent economic crisis raise many questions about the future growth of East Asia. Our analysis of historical experiences shows that low TFP growth in the East Asian newly industrialized economies (NIEs) is a natural pattern of growth at the initial phase of industrialization. Empirical evidence shows that East Asian NIEs in recent decades have been proceeding toward an efficiency-based growth as developed countries did some time ago. The history of Latin America, however, indicates that the reform of old-fashioned institutions is needed if East Asia is to follow the path of the developed countries.
What Would Have Happened in Indonesia if Different Economic Policies Had Been Implemented When the Crisis Started?
Authors: Azis Iwan J.
Published: October 2002

Many models of the Indonesian economy cannot generate the large collapses in output and exchange rate experienced in 1997–98. The model in this paper was able to replicate the actual events by adding several new links. One new link is between the depreciation of the exchange rate and the deterioration of the balance sheets of firms, which are in turn linked to decline in investment. Another new link is between decline in output and decline in business confidence, leading to possible increased capital outflow and exchange rate collapse. The IMF's high interest rate policy did not succeed in strengthening the rupiah because it inflicted such severe damage on the net worth of Indonesian firms that it caused capital flight to accelerate, turning what was originally just a financial crisis into a major recession.

Two alternative counterfactual policy packages are examined: (1) a lower interest rate policy and (2) a lower interest rate policy combined with a partial write-down of the external debt. The model indicates that the country's macroeconomic conditions would have fared better if the prolonged high interest rate policy had been avoided. The results suggest that early actions should have been undertaken to address the mounting private foreign debts. The delayed handling of private debts had prevented other policies from working effectively. The two counterfactual policies also would have resulted in a more favorable outcome for income distribution and poverty incidence. The model revealed a close correlation between worsening (improving) income distribution and increasing (declining) interest rates.