bluuebunny/crossref_metadata_2025 huggingface dataset:
CIRCADIAN RHYTHMS: Basic Neurobiology and Clinical Applications
Authors: Moore MD Robert Y.
Published: July 2002

▪ Abstract  Circadian rhythms are major features of adaptation to our environment. In mammals, circadian rhythms are generated and regulated by a circadian timing system. This system consists of entrainment pathways, pacemakers, and pacemaker output to effector systems that are under circadian control. The primary entrainment pathway is the retinohypothalamic tract, which terminates in the circadian pacemakers, the suprachiasmatic nuclei of the hypothalamus. The output of the suprachiasmatic nuclei is principally to the hypothalamus, the midline thalamus, and the basal forebrain. This provides a temporal organization to the sleep-wake cycle, to many physiological and endocrine functions, and to psychomotor performance functions. Disorders of circadian timing primarily affect entrainment and pacemaker functions. The pineal hormone, melatonin, appears to be a promising agent for therapy of some circadian timing disorders.
LOW-MOLECULAR-WEIGHT HEPARIN: Prophylaxis and Treatment of Venous Thromboembolism
Authors: Pineo, MD Graham F. , Hull, MD Russell D.
Published: July 2002

▪ Abstract  Intravenous heparin followed by warfarin has been the classical anticoagulant therapy of acute venous thromboembolism for the last 30 years. Furthermore, low-dose unfractionated heparin given two to three times daily has been the most popular form of prophylaxis for venous thrombosis. In recent years, a number of low-molecular-weight heparins have become available for clinical trials. These agents have many advantages over unfractionated heparin and are now being used widely internationally for the prevention and treatment of venous thromboembolism. Indeed, low-molecular-weight heparin will undoubtedly replace intravenous unfractionated heparin not only in the treatment of venous thromboembolism, but in other conditions where heparin therapy is indicated. Whether or not the low-molecular-weight heparins can decrease or eliminate some of the complications of unfractionated heparin will depend on the outcome of future clinical trials.
Concept and Evaluation of Hibernating Myocardium
Authors: Rahimtoola, MB, FRCP, MACP Shahbudin H.
Published: July 2002

Hibernating myocardium is a state of persistently impaired myocardial and left ventricular function at rest due to reduced coronary blood flows. It can be defined as an exquisitely regulated tissue successfully adapting its activity to prevailing circumstances. It has been documented in patients with angina (chronic stable and/or unstable), acute myocardial infarction, heart failure and/or severe left ventricular dysfunction, and anomalous left coronary artery from the pulmonary artery. The diagnosis of hibernating myocardium involves (a) documenting left ventricular dysfunction at rest and (b) documenting that there is viable myocardium in the area of dysfunction. Tests commonly used for the latter are dobutamine echocardiography,201Tl isotope studies, and positron image tomography. Revascularization, either by surgery or by interventional catheter techniques, has been shown to improve or normalize the abnormal left ventricular function at rest.
Lymphatic Mapping and Sentinel Lymph Node Biopsy in Patients with Breast Cancer
Authors: Cox Charles E. , Bass Siddharth S. , McCann Christa R. , Ku Ni Ni K. , Berman Claudia , Durand Kara , Bolano Monica , Wang Jessica , Peltz Eric , Cox Sarah , Salud Christopher , Reintgen Douglas S. , Lyman Gary H.
Published: July 2002

▪ Abstract  The standard of care for the evaluation of axillary nodal involvement remains complete lymph node dissection. Lymphatic mapping and sentinel lymph node (SLN) biopsy are changing this long-held paradigm; indeed, several leading institutions already reserve complete axillary dissection for patients with metastasis to the SLN. In addition to reviewing the literature, this chapter describes our lymphatic mapping experience at the H Lee Moffitt Cancer Center and Research Institute with 1147 breast cancer patients. Our results, in addition to a meta-analysis of data from 12 institutions comprising an additional 1842 patients undergoing complete axillary dissection, demonstrate that SLN biopsy is an accurate method of axillary staging. Although the results from small series may exaggerate the probability of false negative results, the risk of nodal disease based on tumor size and other risk factors should be evaluated when considering the results of SLN sampling.
Mechanisms of Cancer Drug Resistance
Authors: Gottesman Michael M.
Published: July 2002

▪ Abstract  The design of cancer chemotherapy has become increasingly sophisticated, yet there is no cancer treatment that is 100% effective against disseminated cancer. Resistance to treatment with anticancer drugs results from a variety of factors including individual variations in patients and somatic cell genetic differences in tumors, even those from the same tissue of origin. Frequently resistance is intrinsic to the cancer, but as therapy becomes more and more effective, acquired resistance has also become common. The most common reason for acquisition of resistance to a broad range of anticancer drugs is expression of one or more energy-dependent transporters that detect and eject anticancer drugs from cells, but other mechanisms of resistance including insensitivity to drug-induced apoptosis and induction of drug-detoxifying mechanisms probably play an important role in acquired anticancer drug resistance. Studies on mechanisms of cancer drug resistance have yielded important information about how to circumvent this resistance to improve cancer chemotherapy and have implications for pharmacokinetics of many commonly used drugs.
XENORHABDUS AND PHOTORHABDUS SPP.: Bugs That Kill Bugs
Authors: Forst Steven , Dowds Barbara , Boemare Noël , Stackebrandt Erko
Published: July 2002

▪ Abstract  Xenorhabdus and Photorhabdus spp. are gram negative gamma proteobacteria that form entomopathogenic symbioses with soil nematodes. They undergo a complex life cycle that involves a symbiotic stage, in which the bacteria are carried in the gut of the nematodes, and a pathogenic stage, in which susceptible insect prey are killed by the combined action of the nematode and the bacteria. Both bacteria produce antibiotics, intracellular protein crystals, and numerous other products. These traits change in phase variants, which arise when the bacteria are maintained under stationary phase conditions in the laboratory. Molecular biological studies suggest that Xenorhabdus and Photorhabdus spp. may serve as valuable model systems for studying signal transduction and transcriptional and posttranscriptional regulation of gene expression. Such studies also indicate that these bacterial groups, which had been previously considered to be very similar, may actually be quite different at the molecular level.
Dopaminergic Modulation of Neuronal Excitability in the Striatum and Nucleus Accumbens
Authors: Nicola Saleem M. , Surmeier D. James , Malenka Robert C.
Published: July 2002

The striatum and its ventral extension, the nucleus accumbens, are involved in behaviors as diverse as motor planning, drug seeking, and learning. Invariably, these striatally mediated behaviors depend on intact dopaminergic innervation. However, the mechanisms by which dopamine modulates neuronal function in the striatum and nucleus accumbens have been difficult to elucidate. Recent electrophysiological studies have revealed that dopamine alters both voltage-dependent conductances and synaptic transmission, resulting in state-dependent modulation of target cells. These studies make clear predictions about how dopamine, particularly via D1 receptor activation, should alter the responsiveness of striatal neurons to extrinsic excitatory synaptic activity.
Natural Image Statistics and Neural Representation
Authors: Simoncelli Eero P , Olshausen Bruno A
Published: July 2002

▪ Abstract  It has long been assumed that sensory neurons are adapted, through both evolutionary and developmental processes, to the statistical properties of the signals to which they are exposed. Attneave (1954) , Barlow (1961) proposed that information theory could provide a link between environmental statistics and neural responses through the concept of coding efficiency. Recent developments in statistical modeling, along with powerful computational tools, have enabled researchers to study more sophisticated statistical models for visual images, to validate these models empirically against large sets of data, and to begin experimentally testing the efficient coding hypothesis for both individual neurons and populations of neurons.
Neurotrophins: Roles in Neuronal Development and Function
Authors: Huang Eric J , Reichardt Louis F
Published: July 2002

▪ Abstract  Neurotrophins regulate development, maintenance, and function of vertebrate nervous systems. Neurotrophins activate two different classes of receptors, the Trk family of receptor tyrosine kinases and p75NTR, a member of the TNF receptor superfamily. Through these, neurotrophins activate many signaling pathways, including those mediated by ras and members of the cdc-42/ras/rho G protein families, and the MAP kinase, PI-3 kinase, and Jun kinase cascades. During development, limiting amounts of neurotrophins function as survival factors to ensure a match between the number of surviving neurons and the requirement for appropriate target innervation. They also regulate cell fate decisions, axon growth, dendrite pruning, the patterning of innervation and the expression of proteins crucial for normal neuronal function, such as neurotransmitters and ion channels. These proteins also regulate many aspects of neural function. In the mature nervous system, they control synaptic function and synaptic plasticity, while continuing to modulate neuronal survival.
LIPASES AND CARBOXYLESTERASES: Possible Roles in the Hepatic Metabolism of Retinol
Authors: Harrison Earl H.
Published: July 2002

▪ Abstract  The formation and hydrolysis of retinyl esters are key processes in the metabolism of the fat-soluble micronutrient vitamin A. Long-chain acyl esters of retinol are the major chemical form of vitamin A (retinoid) stored in the body. Retinyl esters are found in a variety of tissues and cell types, but most of the total body retinoid is accounted for by the retinyl esters stored in the liver. Thus, these esters represent the major endogenous source of retinoid that can be delivered to peripheral tissues for conversion to biologically active forms. This review summarizes current knowledge about the identity, function, and regulation of the hepatic enzymes potentially involved in catalyzing the hydrolysis of retinyl esters. These enzymes include several known and characterized lipases and carboxylesterases. Although there is accumulating evidence that these enzymes function as retinyl ester hydrolases in vitro, it is not clear which play important physiological roles in hepatic retinyl ester metabolism.
NONOXIDATIVE MODIFICATIONS OF LIPOPROTEINS IN ATHEROGENESIS
Authors: Tabas Ira
Published: July 2002

▪ Abstract  The key initiating event in atherosclerosis is the retention of plasma lipoproteins in the subendothelial matrix. Subsequently, a series of biological responses to this retained material leads to specific molecular and cellular processes that promote lesion formation. There is considerable evidence that many of these biological responses, notably macrophage cholesteryl ester loading (foam cell formation), require subendothelial modification of the retained lipoproteins. Oxidation of lipoproteins is one such modification that likely occurs in vivo and promotes certain atherogenic events, but oxidation cannot explain all aspects of atherogenesis, including certain elements of macrophage foam cell formation. For this reason, there has been renewed interest in other modifications of lipoproteins that may be important in atherogenesis. This review addresses five such lipoprotein modifications, namely aggregation, glycation, immune complex formation, proteoglycan complex formation, and conversion to cholesterol-rich liposomes. The focus is on the evidence that these modifications occur in atherosclerotic lesions and on the potential role of these modified lipoproteins in atherogenesis, with an emphasis on macrophage foam cell formation.
HOWHOST-MICROBIALINTERACTIONSSHAPE THENUTRIENTENVIRONMENT OF THEMAMMALIANINTESTINE
Authors: Hooper Lora V. , Midtvedt Tore , Gordon Jeffrey I.
Published: July 2002

▪ Abstract  Humans and other mammals are colonized by a vast, complex, and dynamic consortium of microorganisms. One evolutionary driving force for maintaining this metabolically active microbial society is to salvage energy from nutrients, particularly carbohydrates, that are otherwise nondigestible by the host. Much of our understanding of the molecular mechanisms by which members of the intestinal microbiota degrade complex polysaccharides comes from studies of Bacteroides thetaiotaomicron, a prominent and genetically manipulatable component of the normal human and mouse gut. Colonization of germ-free mice with B. thetaiotaomicron has shown how this anaerobe modifies many aspects of intestinal cellular differentiation/gene expression to benefit both host and microbe. These and other studies underscore the importance of understanding precisely how nutrient metabolism serves to establish and sustain symbiotic relationships between mammals and their bacterial partners.
SIGNAL TRANSDUCTION IN ENVIRONMENTAL NEUROTOXICITY
Authors: Costa L. G.
Published: July 2002

▪ Abstract  Signal transduction is the process by which specific information is transferred from the cell surface to the cytosol and ultimately to the nucleus, leading to changes in gene expression. Since these chains of biochemical and molecular steps control the normal function of each cell, disruption of these processes would have a significant impact on cell physiology. Some of the major signal transduction pathways are briefly reviewed. The interactions of four chemicals (lead, ethanol, polychlorinated biphenyls, and trimethyltin) with different cell signaling systems, particularly the phospholipid hydrolysis/protein kinase C pathway, are discussed. The possible causal relationship of such cellular and molecular interactions with known signs and symptoms of neurotoxicity are highlighted.
Remodeling the Cardiac Sarcomere Using Transgenesis
Authors: Robbins Jeffrey
Published: July 2002

▪ Abstract  An underpinning of basic physiology and clinical medicine is that specific protein complements underlie cell and organ function. In the heart, contractile protein changes correlating with functional alterations occur during both normal development and the development of numerous pathologies. What has been lacking for the majority of these observations is an extension of correlation to causative proof. More specifically, different congenital heart diseases are characterized by shifts in the motor proteins, and the genetic etiologies of a number of different dilated and hypertrophic cardiomyopathies have been established as residing at loci encoding the contractile proteins. To establish cause, or to understand development of the pathophysiology over an animal’s life span, it is necessary to direct the heart to synthesize, in the absence of other pleiotropic changes, the candidate protein. Subsequently one can determine whether or how the protein’s presence causes the effects either directly or indirectly. By affecting the heart’s protein complement in a defined manner, the potential to establish the function of different proteins and protein isoforms exists. Transgenesis provides a means of stably modifying the mammalian genome. By directing expression of engineered proteins to the heart, cardiac contractile protein profiles can be effectively remodeled and the resultant animal used to study the consequences of a single, genetic manipulation at the molecular, biochemical, cytological, and physiological levels.
A Hundred Years of Sodium Pumping
Authors: Glynn Ian M.
Published: July 2002

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▪ Abstract  This article gives a history of the evidence (a) that animal cell membranes contain pumps that expel sodium ions in exchange for potassium ions; (b) that the pump derives energy from the hydrolysis of ATP; (c) that it is thermodynamically reversible—artificially steep transmembrane ion gradients make it run backward synthesizing ATP from ADP and orthophosphate; (d) that its mechanism is a ping-pong one, in which phosphorylation of the pump by ATP is associated with an efflux of three sodium ions, and hydrolysis of the phosphoenzyme is associated with an influx of two potassium ions; (e) that each half of the working cycle involves both the transfer of a phosphate group and a conformational change—the phosphate transfer being associated with the occlusion of ions bound at one surface and the conformational change releasing the occluded ions at the opposite surface.
Fatty Acid Oxidation Disorders
Authors: Rinaldo Piero , Matern Dietrich , Bennett Michael J.
Published: July 2002

▪ Abstract  Genetic disorders of mitochondrial fatty acid β-oxidation have been recognized within the last 20 years as important causes of morbidity and mortality, highlighting the physiological significance of fatty acids as an energy source. Although the mammalian mitochondrial fatty acid-oxidizing system was recognized at the beginning of the last century, our understanding of its exact nature remains incomplete, and new components are being identified frequently. Originally described as a four-step enzymatic process located exclusively in the mitochondrial matrix, we now recognize that long-chain-specific enzymes are bound to the inner mitochondrial membrane, and some enzymes are expressed in a tissue-specific manner.

Much of our new knowledge of fatty acid metabolism has come from the study of patients who were diagnosed with single-gene autosomal recessive defects, a situation that seems to be further evolving with the emergence of phenotypes determined by combinations of multiple genetic and environmental factors. This review addresses the normal process of mitochondrial fatty acid β-oxidation and discusses the clinical, metabolic, and molecular aspects of more than 20 known inherited diseases of this pathway that have been described to date.
VARIABILITY AND GENETIC STRUCTURE OF PLANT VIRUS POPULATIONS
Authors: García-Arenal Fernando , Fraile Aurora , Malpica José M.
Published: July 2002

▪ Abstract  Populations of plant viruses, like all other living beings, are genetically heterogeneous, a property long recognized in plant virology. Only recently have the processes resulting in genetic variation and diversity in virus populations and genetic structure been analyzed quantitatively. The subject of this review is the analysis of genetic variation, its quantification in plant virus populations, and what factors and processes determine the genetic structure of these populations and its temporal change. The high potential for genetic variation in plant viruses, through either mutation or genetic exchange by recombination or reassortment of genomic segments, need not necessarily result in high diversity of virus populations. Selection by factors such as the interaction of the virus with host plants and vectors and random genetic drift may in fact reduce genetic diversity in populations. There is evidence that negative selection results in virus-encoded proteins being not more variable than those of their hosts and vectors. Evidence suggests that small population diversity, and genetic stability, is the rule. Populations of plant viruses often consist of a few genetic variants and many infrequent variants. Their distribution may provide evidence of a population that is undifferentiated, differentiated by factors such as location, host plant, or time, or that fluctuates randomly in composition, depending on the virus.
SURFACEATTACHMENT ANDPRE-PENETRATIONSTAGEDEVELOPMENT BYPLANTPATHOGENICFUNGI
Authors: Tucker Sara L. , Talbot Nicholas J.
Published: July 2002

▪ Abstract  Fungal pathogens cause many of the most serious crop diseases. One of the principal reasons for the success of this group is their ability to locate and perceive appropriate host surfaces and then to elaborate specialized infection structures. Here we review the processes implicated in surface attachment, germ tube elongation, and development of appressoria. The involvement of surface-acting proteins such as fungal hydrophobins and integrins in these processes is evaluated, along with a description of studies that have revealed the existence of conserved signaling pathways that regulate appressorium formation. Finally, we anticipate the prospect of genome-level analysis of fungal pathogens and the key research questions that will need to be addressed.
Assessing the Capacity of Mass Electorates
Authors: Converse Philip E.
Published: July 2002

This is a highly selective review of the huge literature bearing on the capacity of mass electorates for issue voting, in view of the great (mal)distribution of political information across the public, with special attention to the implications of information heterogeneity for alternative methods of research. I trace the twists and turns in understanding the meaning of high levels of response instability on survey policy items from their discovery in the first panel studies of 1940 to the current day. I consider the recent great elaboration of diverse heuristics that voters use to reason with limited information, as well as evidence that the aggregation of preferences so central to democratic process serves to improve the apparent quality of the electoral response. A few recent innovations in design and analysis hold promise of illuminating this topic from helpful new angles.

Never overestimate the information of the American electorate, but never underestimate its intelligence.

(Mark Shields, syndicated political columnist, citing an old aphorism)
BIASES IN THE INTERPRETATION AND USE OF RESEARCH RESULTS
Authors: MacCoun Robert J.
Published: July 2002

▪ Abstract  The latter half of this century has seen an erosion in the perceived legitimacy of science as an impartial means of finding truth. Many research topics are the subject of highly politicized dispute; indeed, the objectivity of the entire discipline of psychology has been called into question. This essay examines attempts to use science to study science: specifically, bias in the interpretation and use of empirical research findings. I examine theory and research on a range of cognitive and motivational mechanisms for bias. Interestingly, not all biases are normatively proscribed; biased interpretations are defensible under some conditions, so long as those conditions are made explicit. I consider a variety of potentially corrective mechanisms, evaluate prospects for collective rationality, and compare inquisitorial and adversarial models of science.
JUDGMENT AND DECISION MAKING
Authors: Mellers B. A. , Schwartz A. , Cooke A. D. J.
Published: July 2002

▪ Abstract  For many decades, research in judgment and decision making has examined behavioral violations of rational choice theory. In that framework, rationality is expressed as a single correct decision shared by experimenters and subjects that satisfies internal coherence within a set of preferences and beliefs. Outside of psychology, social scientists are now debating the need to modify rational choice theory with behavioral assumptions. Within psychology, researchers are debating assumptions about errors for many different definitions of rationality. Alternative frameworks are being proposed. These frameworks view decisions as more reasonable and adaptive than previously thought. For example, “rule following.” Rule following, which occurs when a rule or norm is applied to a situation, often minimizes effort and provides satisfying solutions that are “good enough,” though not necessarily the best. When rules are ambiguous, people look for reasons to guide their decisions. They may also let their emotions take charge. This chapter presents recent research on judgment and decision making from traditional and alternative frameworks.
The Pain of Being Sick: Implications of Immune-to-Brain Communication for Understanding Pain
Authors: Watkins L. R. , Maier S. F.
Published: July 2002

This review focuses on the powerful pain facilitatory effects produced by the immune system. Immune cells, activated in response to infection, inflammation, or trauma, release proteins called proinflammatory cytokines. These proinflammatory cytokines signal the central nervous system, thereby creating exaggerated pain as well as an entire constellation of physiological, behavioral, and hormonal changes. These changes are collectively referred to as the sickness response. Release of proinflammatory cytokines by immune cells in the body leads, in turn, to release of proinflammatory cytokines by glia within the brain and spinal cord. Evidence is reviewed supporting the idea that proinflammatory cytokines exert powerful pain facilitatory effects following their release in the body, in the brain, and in the spinal cord. Such exaggerated pain states naturally occur in situations involving infection, inflammation, or trauma of the skin, of peripheral nerves, and of the central nervous system itself. Implications for human pain conditions are discussed.
Should We Use a Case-Crossover Design?
Authors: Maclure M. , Mittleman and M. A.
Published: July 2002

▪ Abstract  The first decade of experience with case-crossover studies has shown that the design applies best if the exposure is intermittent, the effect on risk is immediate and transient, and the outcome is abrupt. However, this design has been used to study single changes in exposure level, gradual effects on risk, and outcomes with insidious onsets. To estimate relative risk, the exposure frequency during a window just before outcome onset is compared with exposure frequencies during control times rather than in control persons. One or more control times are supplied by each of the cases themselves, to control for confounding by constant characteristics and self-confounding between the trigger's acute and chronic effects. This review of published case-crossover studies is designed to help the reader prepare a better research proposal by understanding triggers and deterrents, target person times, alternative study bases, crossover cohorts, induction times, effect and hazard periods, exposure windows, the exposure opportunity fallacy, a general likelihood formula, and control crossover analysis.
Dietary Interventions to Prevent Disease
Authors: Bowen Deborah J. , Beresford Shirley A. A.
Published: July 2002

▪ Abstract  Changing dietary behaviors to prevent chronic disease has been an important research focus for the last 25 years. Here we present a review of published articles on the results of research to identify methods to change key dietary habits: fat intake, fiber intake, and consumption of fruits and vegetables. We divided the research reviewed into sections, based on the channel through which the intervention activities were delivered. We conclude that the field is making progress in identifying successful dietary change strategies, but that more can be learned. Particularly, we need to transfer some of the knowledge from the individual-based trials to community-level interventions. Also, more research with rigorous methodology must be done to test current and future intervention options.
GENDER AND SEXUAL HARASSMENT
Authors: Welsh Sandy
Published: July 2002

▪ Abstract  Research on sexual harassment is still in its infancy. Over the past 20 years, research has moved from prevalence studies to more sophisticated empirical and theoretical analyses of the causes and consequences of sexual harassment. This review provides an overview of the prevalence and measurement of harassment along with some suggestions for developing standard measures of sexual harassment. Researchers are encouraged to include organizational forms of harassment in their measures, along with commonly understood individual forms. The most prominent and promising explanations of harassment are discussed including societal, organizational, and individual level approaches. Of particular promise are approaches incorporating the gendered nature of organizational structures and processes. Research on the responses to and consequences of sexual harassment are also presented. The review ends with a discussion of overlooked areas and directions for future research, including the need for more advanced survey data collection techniques and qualitative research.
Adenoviral Activin A Expression Prevents Intimal Hyperplasia in Human and Murine Blood Vessels by Maintaining the Contractile Smooth Muscle Cell Phenotype
Authors: Engelse Marten A. , Lardenoye JanWillem H.P. , Neele Jolanda M. , Grimbergen Jos M. , de Vries Margreet R. , Lamfers Martine L.M. , Pannekoek Hans , Quax Paul H.A. , de Vries Carlie J.M.
Published: July 2002

Activin A alters the characteristics of human arterial smooth muscle cells (SMCs) toward a contractile, quiescent phenotype. We hypothesize that activin A may prevent SMC-rich neointimal hyperplasia. Here, we study the effect of adenovirus-mediated expression of activin A on neointima formation in vitro and in vivo. Human saphenous vein organ cultures, in which a neointima is formed spontaneously, were infected either with activin A- or lacZ-adenovirus. Activin A-overexpression reduces neointima formation by 78%, whereas no significant reduction was observed after control infection. In addition, the effect of activin A on neointima formation was assessed in vivo in mice with cuffed femoral arteries. In activin A adenovirus-infected mice (IV injection), neointimal hyperplasia is reduced by 77% compared with the SMC-rich neointima in mock-infected or in noninfected mice. Cultured human saphenous vein SMCs and murine aorta SMCs were incubated with activin A and an increased expression of SM22α and SM α-actin mRNA, and SM α-actin protein was demonstrated. Laser-capture microdissection on sections of cuffed murine arteries and subsequent real-time RT-PCR established in vivo induction of SM α-actin mRNA in the media of activin A–treated mice. In summary, activin A inhibits neointima formation in vitro and in vivo by preventing SMC dedifferentiation.
The Prudent Professionalism of George Herbert Walker Bush
Authors: Greenstein Fred I.
Published: July 2002

Just as the pre-presidential George Bush was described as a public servant who left no footprints, it is tempting to conclude that President Bush accomplished little or nothing during his time in the White House. In fact, he presided over the end of the Cold War and the largest United States military action since the Vietnam War, as well as a number of domestic achievements. Future presidents can derive positive lessons from Bush's often impressive political tactics, as well as cautions from his costly failures to make effective use of the bully pulpit and identify himself with a particular vision of the nation's future.
Oulipo | vs | Recombinant Poetics
Authors: Seaman Bill
Published: July 2002

This paper compares and contrasts approaches to combinatorics in OULIPO and Recombinant Poetics. OULIPO, also known as Ouvroir de Litérature Potentielle, is a literary and artistic association founded in the 1960s whose combinatoric methods and experimental concepts continue to be generative and relevant to this day. Recombinant Poetics is a term that I coined in 1995 in order to define a particular approach to emergent meaning that is used in generative virtual environments and other computer-based combinatoric media forms. Combinatoric works enable the exploration of sets of media elements in different orders and combinations. The meaning of such work is derived through dynamic interaction. Another group exploring combinatorics uses digital audio techniques. The abbreviation “VS” (“versus”) is often used in techno-audio remix culture to designate the remix of one group's music by another, often having only an oblique relation to the original.
Arabic Hypocoristics and the Status of the Consonantal Root
Authors: Davis Stuart , Zawaydeh Bushra Adnan
Published: July 2002

There is currently a controversy regarding the lexical (morphemic) status of the consonantal root in the Semitic languages. Bat-El (1994) and Ratcliffe (1997) have argued against the lexical status of the consonantal root in Hebrew and Arabic, respectively. However, Prunet, Béland, and Idrissi (2000) present Arabic aphasic evidence supporting the lexical (morphemic) status of the consonantal root for Arabic. In this article we offer supporting evidence from Arabic hypocoristics for the morphemic status of the consonantal root. We argue that hypocoristic formation is an output-to-output word formation process that nonetheless references the consonantal root. We then discuss implications.
Anatomical Segregation of Component Processes in an Inductive Inference Task
Authors: Goel Vinod , Dolan Raymond J.
Published: July 2002

Inductive inference underlies much of human cognition. The essential component of induction is hypothesis selection based on some criterion of relevance. The purpose of this study was to determine the neural substrate of inductive inference, particularly hypothesis selection, using fMRI. Ten volunteers were shown stimuli consisting of novel animals under two task conditions, and asked to judge whether all the animals in the set were the same type of animal. In one condition, subjects were given a rule that specified the criteria for “same type of animal.” In the other condition, subjects had to infer the rule without instruction. The two conditions were further factored into easy and difficult components. Rule inference was specifically associated with bilateral hippocampal activation while the task by difficulty interaction was associated with activation in right lateral orbital prefrontal cortex. We interpret the former in terms of semantic encoding of novel stimuli, and the latter in terms of hypothesis selection. Thus, we show an anatomical dissociation between task implementation and task difficulty that may correspond to a critical psychological distinction in the processes necessary for inductive inference.
Incomplete Gustatory Lateralization as Shown by Analysis of Taste Discrimination After Callosotomy
Authors: Aglioti Salvatore , Tassinari Giancarlo , Corballis Michael C. , Berlucchi Giovanni
Published: July 2002

The lateral organization of the gustatory pathway in man is incompletely understood. Majority of the studies support an uncrossed projection from each side of the tongue to the cortex, but reports of an opposite crossed organization continue to appear in the neurological literature. We studied the lateral organization of the gustatory pathway in normal controls, a man with a complete callosal agenesis, and a man with a complete section of the corpus callosum, a right anterior-frontal lesion, and language in the left hemisphere. Sapid solutions were applied to one or the other side of the tongue, and subjects reported the taste of the stimulus either verbally or by manually pointing to the name of the taste. There were no differences in accuracy and reaction time between the right and left hemitongues of the controls and the genetically acallosal observer. By contrast, the callosotomy subject showed a constant marked advantage of the left hemitongue over the right for both accuracy and speed of response, though performance with right stimuli was clearly above chance. The left advantage can be attributed to the left hemisphere being favored by the essentially verbal nature of the task, or to the presence of a lesion in cortical gustatory areas in the right hemisphere, or to both factors. Whichever of these hypotheses turns out to be correct, the results unequivocally reject the notion of an exclusively crossed organization of the gustatory pathway from the tongue to the cortex, and favor the notion of a bilaterally distributed organization of this pathway with a marked predominance of the uncrossed over the crossed component.
Coupled Temporal Memories in Parkinson's Disease: A Dopamine-Related Dysfunction
Authors: Malapani Chara , Rakitin Brian , Levy R. , Meck Warren H. , Deweer Bernard , Dubois Bruno , Gibbon John
Published: July 2002

Dysfunction of the basal ganglia and the brain nuclei interconnected with them leads to disturbances of movement and cognition, including disordered timing of movement and perceptual timing deflcits. Patients with Parkinson's disease (PD) were studied in temporal reproduction tasks. We examined PD patients when brain dopamine (DA) transmission was impaired (OFF state) and when DA transmission was reestablished, at the time of maximal clinical beneflt following administration of levodopa + apomorphine (ON state). Patients reproduced target times of 8 and 21 sec trained in blocked trials with the peak interval procedure, which were veridical in the ON state, comparable to normative performance by healthy young and aged controls (Experiment 1). In the OFF state, temporal reproduction was impaired in both accuracy and precision (variance). The 8-sec signal was reproduced as longer and the 21-sec signal was reproduced as shorter than they actually were (Experiment 1). This fimigrationfl effect was dependent upon training of two different durations. When PD patients were trained on 21 sec only (Experiment 2), they showed a reproduction error in the long direction, opposite to the error produced under the dual training condition of Experiment 1. The results are discussed as a mutual attraction between temporal processing systems, in memory and clock stages, when dopaminergic regulation in the striatum is dysfunctional.
Cerebral Mechanisms of Hypnotic Induction and Suggestion
Authors: Rainville Pierre , Hofbauer Robert K. , Paus Tomáš , Duncan Gary H. , Bushnell M. Catherine , Price Donald D.
Published: July 2002

The neural mechanisms underlying hypnotic states and responses to hypnotic suggestions remain largely unknown and, to date, have been studied only with indirect methods. Here, the effects of hypnosis and suggestions to alter pain perception were investigated in hypnotizable subjects by using positron emission tomography (PET) measures of regional cerebral blood flow (rCBF) and electroencephalographic (EEG) measures of brain electrical activity. The experimental conditions included a restful state (Baseline) followed by hypnotic relaxation alone (Hypnosis) and by hypnotic relaxation with suggestions for altered pain unpleasantness (Hypnosis-with-Suggestion). During each scan, the left hand was immersed in neutral (35°C) or painfully hot (47°C) water in the first two conditions and in painfully hot water in the last condition. Hypnosis was accompanied by significant increases in both occipital rCBF and delta EEG activity, which were highly correlated with each other (r = 0.70, p < 0.0001). Peak increases in rCBF were also observed in the caudal part of the right anterior cingulate sulcus and bilaterally in the inferior frontal gyri. Hypnosis-related decreases in rCBF were found in the right inferior parietal lobule, the left precuneus, and the posterior cingulate gyrus. Hypnosis-with-suggestions produced additional widespread increases in rCBF in the frontal cortices predominantly on the left side. Moreover, the medial and lateral posterior parietal cortices showed suggestion-related increases overlapping partly with regions of hypnosis-related decreases. Results support a state theory of hypnosis in which occipital increases in rCBF and delta activity reflect the alteration of consciousness associated with decreased arousal and possible facilitation of visual imagery. Frontal increases in rCBF associated with suggestions for altered perception might reflect the verbal mediation of the suggestions, working memory, and top-down processes involved in the reinterpretation of the perceptual experience. These results provide a new description of the neurobiological basis of hypnosis, demonstrating specific patterns of cerebral activation associated with the hypnotic state and with the processing of hypnotic suggestions.
Population Dynamics of Spiking Neurons: Fast Transients, Asynchronous States, and Locking
Authors: Gerstner Wulfram
Published: July 2002

An integral equation describing the time evolution of the population activity in a homogeneous pool of spiking neurons of the integrate-and-fire type is discussed. It is analytically shown that transients from a state of incoherent firing can be immediate. The stability of incoherent firing is analyzed in terms of the noise level and transmission delay, and a bifurcation diagram is derived. The response of a population of noisy integrate-and-fire neurons to an input current of small amplitude is calculated and characterized by a linear filter L. The stability of perfectly synchronized “locked” solutions is analyzed.
Period Focusing Induced by Network Feedback in Populations of Noisy Integrate-and-Fire Neurons
Authors: Rodríguez Francisco B. , Suárez Alberto , López Vicente
Published: July 2002

The population dynamics of an ensemble of nonleaky integrate-and-fire stochastic neurons is studied. The model selected allows for a detailed analysis of situations where noise plays a dominant role. Simulations in a regime with weak to moderate interactions show that a mechanism of excitatory message interchange among the neurons leads to a decrease in the firing period dispersion of the individual units. The dispersion reduction observed is larger than what would be expected from the decrease in the period. This ‘period focusing’ is explained using a mean-field model. It is a dynamical effect that arises from the progressive decrease of the effective firing threshold as a result of the messages received by each unit from the rest of the population. A back-of-the-envelope formula to calculate this nontrivial dispersion reduction and a simple geometrical description of the effect are also provided.
Population Computation of Vectorial Transformations
Authors: Baraduc Pierre , Guigon Emmanuel
Published: July 2002

Many neurons of the central nervous system are broadly tuned to some sensory or motor variables. This property allows one to assign to each neuron a preferred attribute (PA). The width of tuning curves and the distribution of PAs in a population of neurons tuned to a given variable define the collective behavior of the population. In this article, we study the relationship of the nature of the tuning curves, the distribution of PAs, and computational properties of linear neuronal populations. We show that noise-resistant distributed linear algebraic processing and learning can be implemented by a population of cosine tuned neurons assuming a nonuniform but regular distribution of PAs. We extend these results analytically to the noncosine tuning and uniform distribution case and show with a numerical simulation that the results remain valid for a nonuniform regular distribution of PAs for broad noncosine tuning curves. These observations provide a theoretical basis for modeling general nonlinear sensorimotor transformations as sets of local linearized representations.
Efficient Adaptive Learning for Classification Tasks with Binary Units
Authors: Moreno J. Manuel Torres , Gordon Mirta B.
Published: July 2002

This article presents a new incremental learning algorithm for classification tasks, called Net Lines, which is well adapted for both binary and real-valued input patterns. It generates small, compact feedforward neural networks with one hidden layer of binary units and binary output units. A convergence theorem ensures that solutions with a finite number of hidden units exist for both binary and real-valued input patterns. An implementation for problems with more than two classes, valid for any binary classifier, is proposed. The generalization error and the size of the resulting networks are compared to the best published results on well-known classification benchmarks. Early stopping is shown to decrease overfitting, without improving the generalization performance.
Can Hebbian Volume Learning Explain Discontinuities in Cortical Maps?
Authors: Mitchison Graeme J. , Swindale Nicholas V.
Published: July 2002

It has recently been shown that orientation and retinotopic position, both of which are mapped in primary visual cortex, can show correlated jumps (Das & Gilbert, 1997). This is not consistent with maps generated by Kohonen's algorithm (Kohonen, 1982), where changes in mapped variables tend to be anticorrelated. We show that it is possible to obtain correlated jumps by introducing a Hebbian component (Hebb, 1949) into Kohonen's algorithm. This corresponds to a volume learning mechanism where synaptic facilitation depends not only on the spread of a signal from a maximally active neuron but also requires postsynaptic activity at a synapse. The maps generated by this algorithm show discontinuities across which both orientation and retinotopic position change rapidly, but these regions, which include the orientation singularities, are also aligned with the edges of ocular dominance columns, and this is not a realistic feature of cortical maps. We conclude that cortical maps are better modeled by standard, non-Hebbian volume learning, perhaps coupled with some other mechanism (e.g., that of Ernst, Pawelzik, Tsodyks, & Sejnowski, 1999) to produce receptive field shifts.
Network Stability from Activity-Dependent Regulation of Neuronal Conductances
Authors: Golowasch Jorge , Casey Michael , Abbott L. F. , Marder Eve
Published: July 2002

Activity-dependent plasticity appears to play an important role in the modification of neurons and neural circuits that occurs during development and learning. Plasticity is also essential for the maintenance of stable patterns of activity in the face of variable environmental and internal conditions. Previous theoretical and experimental results suggest that neurons stabilize their activity by altering the number or characteristics of ion channels to regulate their intrinsic electrical properties. We present both experimental and modeling evidence to show that activity-dependent regulation of conductances, operating at the level of individual neurons, can also stabilize network activity. These results indicate that the stomatogastric ganglion of the crab can generate a characteristic rhythmic pattern of activity in two fundamentally different modes of operation. In one mode, the rhythm is strictly conditional on the presence of neuromodulatory afferents from adjacent ganglia. In the other, it is independent of neuromodulatory input but relies on newly developed intrinsic properties of the component neurons.