bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetics of Chemotaxis and Thermotaxis in the Nematode Caenorhabditis Elegans
Authors: Mori Ikue
Published: July 2002

▪ Abstract  Molecular genetic analysis of chemotaxis and thermotaxis in Caenorhabditis elegans has revealed the molecular bases of olfaction, taste, and thermosensation, which, in turn, has demonstrated that sensory signaling in C. elegans is very similar to that in vertebrates. A cyclic nucleotide-gated channel (TAX-2/TAX-4) that is highly homologous to the olfactory and photoreceptor channels in vertebrates is required for taste and thermosensation, in addition to olfaction. A cation channel (OSM-9) that is closely related to a capsaicin receptor channel is required for olfactory adaptation in one olfactory neuron and olfactory sensation in the other olfactory neuron. A novel Gα protein (ODR-3) is essential for olfactory responses in all olfactory neurons and aversive responses in a polymodal sensory neuron. A G protein–coupled seven-transmembrane receptor (ODR-10) is the first olfactory receptor whose ligand was elucidated. Using chemotaxis and thermotaxis as behavioral paradigms, neural plasticity including learning and memory can be studied genetically in C. elegans.
CELLULAR RESPONSES TO INTERFERON-γ
Authors: Boehm U. , Klamp T. , Groot M. , Howard J. C.
Published: July 2002

The phytohemagglutinin-induced virus-inhibitor may, however, be produced in white cells in response to a stimulation of cellular RNA synthesis and may be a feedback mechanism for control of RNA synthesis. E. Frederick Wheelock (1965)

▪ Abstract  Interferons are cytokines that play a complex and central role in the resistance of mammalian hosts to pathogens. Type I interferon (IFN-α and IFN-β) is secreted by virus-infected cells. Immune, type II, or γ-interferon (IFN-γ) is secreted by thymus-derived (T) cells under certain conditions of activation and by natural killer (NK) cells. Although originally defined as an agent with direct antiviral activity, the properties of IFN-γ include regulation of several aspects of the immune response, stimulation of bactericidal activity of phagocytes, stimulation of antigen presentation through class I and class II major histocompatibility complex (MHC) molecules, orchestration of leukocyte-endothelium interactions, effects on cell proliferation and apoptosis, as well as the stimulation and repression of a variety of genes whose functional significance remains obscure. The implementation of such a variety of effects by a single cytokine is achieved by complex patterns of cell-specific gene regulation: Several IFN-γ-regulated genes are themselves components of transcription factors. The IFN-γ response is itself regulated by interaction with responses to other cytokines including IFN-α/β, TNF-α, and IL-4. Over 200 genes are now known to be regulated by IFN-γ and they are listed in a World Wide Web document that accompanies this review. However, much of the cellular response to IFN-γ can be described in terms of a set of integrated molecular programs underlying well-defined physiological systems, for example the induction of efficient antigen processing for MHC-mediated antigen presentation, which play clearly defined roles in pathogen resistance. A promising approach to the complexity of the IFN-γ response is to extend the analysis of the less understood IFN-γ-regulated genes in terms of molecular programs functional in pathogen resistance.
THE ORIGIN OF HODGKIN AND REED/STERNBERG CELLS IN HODGKIN'S DISEASE
Authors: Küppers Ralf , Rajewsky Klaus
Published: July 2002

▪ Abstract  One of the characteristic features of Hodgkin's disease (HD) is the presence of a small population of often bizarre-looking large mono- or multinucleated Hodgkin and Reed-Sternberg (HRS) cells within the affected tissue. Recent cytogenetic investigations, studies of Epstein-Barr virus (EBV) genomes present in HRS cells, and analyses of Ig gene rearrangements amplified from single, micromanipulated HRS cells show that these cells largely represent clonal populations. The finding of Ig gene rearrangements in HRS cells in most cases of HD identifies B cells as the precursors of HRS cells in most if not all cases. Furthermore, the presence and pattern of somatic mutations within the rearranged Ig genes show that HRS cells in classical (i.e. nodular sclerosis, mixed cellularity, and lymphocyte depletion HD) as well as lymphocyte predominant (LP) HD originate from germinal center (GC) B cells. Ongoing somatic mutation and evidence for selection link HRS cells from LP HD to a mutating, antigen-selected GC B cell. In classical HD, the finding of “crippling” mutations and lack of stringent selection for antigen receptor expression suggests that in this case HRS cells are derived from a compartment of GC B cells that were destined to die but escaped apoptosis by some transforming event. One candidate for the latter is EBV infection.
γδ Cells: A Right Time and a Right Place for a Conserved Third Way of Protection
Authors: Hayday Adrian C.
Published: July 2002

The tripartite subdivision of lymphocytes into B cells, αβ T cells, and γδ cells has been conserved seemingly since the emergence of jawed vertebrates, more than 450 million years ago. Yet, while we understand much about B cells and αβ T cells, we lack a compelling explanation for the evolutionary conservation of γδ cells. Such an explanation may soon be forthcoming as advances in unraveling the biochemistry of γδ cell interactions are reconciled with the abnormal phenotypes of γδ-deficient mice and with the striking differences in γδ cell activities in different strains and species. In this review, the properties of γδ cells form a basis for understanding γδ cell interactions with antigens and other cells that in turn form a basis for understanding immunoprotective and regulatory functions of γδ cells in vivo. We conclude by considering which γδ cell functions may be most critical.
IRF Family of Transcription Factors as Regulators of Host Defense
Authors: Taniguchi Tadatsugu , Ogasawara Kouetsu , Takaoka Akinori , Tanaka Nobuyuki
Published: July 2002

Interferon regulatory factors (IRFs) constitute a family of transcription factors that commonly possess a novel helix-turn-helix DNA-binding motif. Following the initial identification of two structurally related members, IRF-1 and IRF-2, seven additional members have now been reported. In addition, virally encoded IRFs, which may interfere with cellular IRFs, have also been identified. Thus far, intensive functional analyses have been done on IRF-1, revealing a remarkable functional diversity of this transcription factor in the regulation of cellular response in host defense. Indeed, IRF-1 selectively modulates different sets of genes, depending on the cell type and/or the nature of cellular stimuli, in order to evoke appropriate responses in each. More recently, much attention has also been focused on other IRF family members. Their functional roles, through interactions with their own or other members of the family of transcription factors, are becoming clearer in the regulation of host defense, such as innate and adaptive immune responses and oncogenesis.
RECENT LIQUID CRYSTAL MATERIAL DEVELOPMENT FOR ACTIVE MATRIX DISPLAYS
Authors: Tarumi K. , Bremer M. , Geelhaar T.
Published: July 2002

▪ Abstract  The structural dependence of the optical and dielectric physical properties of liquid crystal (LC) materials is investigated with the aid of molecular modeling. A material characterization of LC materials is made using fundamental physical measurement values, e.g. optical, dielectric, elastic, and viscous parameters. A novel mixture design based on selected LC materials leads to significant improvements that fulfill the requirements for active matrix LC displays, for instance, fast switching times, lower power consumption, and wide operation temperature ranges. The development of LC displays from the material supplier's point of view is briefly reviewed.
Neuromuscular Control of the Oropharynx and Esophagus in Health and Disease
Authors: Conklin J. L. , Christensen J.
Published: July 2002

The oropharynx and esophagus convey swallowed materials from the mouth to the stomach and protect the airways from aspiration. These functions are subserved by complex neuromuscular interactions that coordinate the timing of the peristaltic contractions of the swallowing organs. The oropharynx and upper esophagus are composed of striated muscle, whereas the distal esophagus is composed of smooth muscle. The central nervous system completely controls peristalsis in the striated muscle organs. In the distal esophagus, neuromuscular mechanisms intrinsic to the esophagus control peristalsis. Diseases of the striated muscle, of the smooth muscle, or of the nervous system can lead to a derangement of peristalsis and disrupt the propulsion of swallowed materials to the stomach.
Natural History of Autosomal Dominant Polycystic Kidney Disease
Authors: Fick Godela M. , Gabow Patricia A.
Published: July 2002

At least two different genes, which have been mapped to chromosomes 4 and 16, cause autosomal dominant polycystic kidney disease, a disorder with renal and extrarenal manifestations. Although gene-linkage testing is possible, the disease is diagnosed mainly through ultrasonography. Renal disease is characterized clinically by hypertension, acute and chronic pain, and variable progression to end-stage renal disease. Extrarenal manifestations include liver cysts, which may lead to complications; ruptured intracranial aneurysms; cardiac valvular disease; colonic diverticula; and inguinal hernias. Disease management is directed at minimizing and treating the complications of this illness.
TOWARD CYSTIC FIBROSIS GENE THERAPY
Authors: Wagner, MD, PhD John A. , Gardner, MD Phyllis
Published: July 2002

▪ Abstract  Cystic fibrosis (CF) is a common genetic disorder characterized by defective epithelial chloride transport and progressive lung disease. Although great strides have been made in the treatment of CF, it remains lethal, often by early adulthood. CF is one of the most extensively researched genetic diseases as a target for gene therapy development. It may also serve as an important model for gene therapy of other diseases. Preclinical and clinical research has lead to the rapid development of a variety of vectors designed to correct the basic defect in CF, including adenovirus, adeno-associated virus, and liposomes. Clinical studies have identified the host immune response and low vector efficiency as key impediments to effective CF gene therapy. Further research promises to refine vector technology and bring CF gene therapy to the bedside.
MAKING AND BREAKING DISULFIDE BONDS
Authors: Raina S. , Missiakas D.
Published: July 2002

▪ Abstract  It is now well established that protein folding requires the assistance of folding helpers in vivo. The formation or isomerization of disulfide bonds in proteins is a slow process requiring catalysis. In nascent polypeptide chains the cysteine residues are in the thiol form. The formation of the disulfide bonds usually occurs simultaneously with the folding of the polypeptide, which means in the endoplasmic reticulum of eukaryotes or in the periplasm of Gram-negative bacteria. In prokaryotes, the existence of redox proteins involved in the formation of disulfide bonds containing proteins has recently been revealed in the periplasm. The discovery of these redox proteins through various genetic approaches will be summarized, as well as the most recent insights regarding their biochemical and biological activities.
SYNTHESIS OF ENANTIOPURE EPOXIDES THROUGH BIOCATALYTIC APPROACHES
Authors: Archelas A. , Furstoss R.
Published: July 2002

▪ Abstract  Enantiopure epoxides, as well as their corresponding vicinal diols, are valuable intermediates in fine organic synthesis, in particular for the preparation of biologically active compounds. The necessity of preparing such target molecules in an optically pure form has triggered much research, leading to the emergence of various new methods based on either conventional chemistry or enzymatically catalyzed reactions. In this review, we focus on the biocatalytic approaches, which include direct epoxidation of olefinic double bonds as well as indirect biocatalytic methods, and which allow for the synthesis of these important chiral building blocks in enantiomerically enriched or even enantiopure form.
THE HIV-1 REV PROTEIN
Authors: Pollard Victoria W. , Malim Michael H.
Published: July 2002

▪ Abstract  The nuclear export of intron-containing HIV-1 RNA is critically dependent on the activity of Rev, a virally encoded sequence-specific RNA-binding protein. Rev shuttles between the nucleus and the cytoplasm and harbors both a nuclear localization signal and a nuclear export signal. These essential peptide motifs have now been shown to function by accessing cellular signal-mediated pathways for nuclear import and nuclear export. HIV-1 Rev therefore represents an excellent system with which to study aspects of transport across the nuclear envelope.
Roles of Thiol-Redox Pathways in Bacteria
Authors: Ritz Daniel , Beckwith Jon
Published: July 2002

▪ Abstract  Disulfide bonds in proteins play various important roles. They are either formed as structural features to stabilize the protein or are found only transiently as part of a catalytic or regulatory cycle. In vivo, the formation and reduction of disulfide bonds is catalyzed by specialized thiol-disulfide exchanging enzymes that contain an active site with the sequence motif Cys-X-X-Cys. These proteins have structurally evolved to catalyze predominantly either oxidative reactions or reductive steps. There is mounting evidence that, in addition to the thiol redox potential, the spatial distribution within different cell compartments and the overall redox state of the cell are equally important. In the cytoplasm, multiple pathways play overlapping roles in the reduction of disulfide bonds and additionally, the expression of several components of thiol-redox pathways was shown to respond to the changes in the cellular thiol-redox equilibrium. In the periplasm, two systems coexist, one catalyzing thiol oxidation and the other disulfide reduction. Recent results suggest that two different mechanisms are used to translocate reducing power from the cytoplasm or to dissipate the electrons after oxidation.
MICROGLIA AS MEDIATORS OF INFLAMMATORY AND DEGENERATIVE DISEASES
Authors: González-Scarano F. , Baltuch Gordon
Published: July 2002

▪ Abstract  Microglia are the principal immune cells in the central nervous system (CNS) and have a critical role in host defense against invading microorganisms and neoplastic cells. However, as with immune cells in other organs, microglia may play a dual role, amplifying the effects of inflammation and mediating cellular degeneration as well as protecting the CNS. In entities like human immunodeficiency virus (HIV) infection of the nervous system, microglia are also critical to viral persistence. In this review we discuss the role of microglia in three diseases in which their activity is at least partially deleterious: HIV, multiple sclerosis, and Alzheimer's disease.
Neural Mechanisms of Orientation Selectivity in the Visual Cortex
Authors: Ferster David , Miller Kenneth D.
Published: July 2002

The origin of orientation selectivity in the responses of simple cells in cat visual cortex serves as a model problem for understanding cortical circuitry and computation. The feed-forward model posits that this selectivity arises simply from the arrangement of thalamic inputs to a simple cell. Much evidence, including a number of recent intracellular studies, supports a primary role of the thalamic inputs in determining simple cell response properties, including orientation tuning. This mechanism alone, however, cannot explain the invariance of orientation tuning to changes in stimulus contrast. Simple cells receive push-pull inhibition: ON inhibition in OFF subregions and vice versa. Addition of such inhibition to the feed-forward model can account for this contrast invariance, provided the inhibition is sufficiently strong. The predictions of “normalization” and “feedback” models are reviewed and compared with the predictions of this modified feed-forward model and with experimental results. The modified feed-forward and the feedback models ascribe fundamentally different functions to cortical processing.
Parallel Pathways for Spectral Coding in Primate Retina
Authors: Dacey Dennis M.
Published: July 2002

The primate retina is an exciting focus in neuroscience, where recent data from molecular genetics, adaptive optics, anatomy, and physiology, together with measures of human visual performance, are converging to provide new insights into the retinal origins of color vision. Trichromatic color vision begins when the image is sampled by short- (S), middle- (M) and long- (L) wavelength-sensitive cone photoreceptors. Diverse retinal cell types combine the cone signals to create separate luminance, red-green, and blue-yellow pathways. Each pathway is associated with distinctive retinal architectures. Thus a blue-yellow pathway originates in a bistratified ganglion cell type and associated interneurons that combine excitation from S cones and inhibition from L and M cones. By contrast, a red-green pathway, in which signals from L and M cones are opposed, is associated with the specialized anatomy of the primate fovea, in which the “midget” ganglion cells receive dominant excitatory input from a single L or M cone.
GAMMA-RAY ASTRONOMY WITH IMAGING ATMOSPHERIC ČERENKOV TELESCOPES
Authors: Aharonian Felix A. , Akerlof Carl W.
Published: July 2002

▪ Abstract  A new generation of imaging atmospheric Čerenkov telescope arrays with energy thresholds as low as 30 GeV, angular resolutions of a few arc minutes, energy resolutions better than 20%, and energy flux sensitivities ∼10−13erg cm−2s−1will elevate ground-based gamma-ray astronomy to a level comparable to that of research at longer wavelengths. The recent exciting observational results as well as theoretical predictions supply a strong rationale for the systematic study of primary γ-radiation in the very-high-energy (VHE) domain and the investigation of ultrarelativistic processes in astrophysical settings on both galactic and extragalactic scales. Such efforts will provide crucial insight into a number of fundamental problems of modern astrophysics and cosmology. This review discusses the current status of the field, the technical improvements that can be achieved, and the astrophysical topics that will be investigated.
HOMOCYSTEINE METABOLISM
Authors: Selhub J.
Published: July 2002

▪ Abstract  Homocysteine is a sulfur amino acid whose metabolism stands at the intersection of two pathways: remethylation to methionine, which requires folate and vitamin B12 (or betaine in an alternative reaction); and transsulfuration to cystathionine, which requires pyridoxal-5′-phosphate. The two pathways are coordinated by S-adenosylmethionine, which acts as an allosteric inhibitor of the methylenetetrahydrofolate reductase reaction and as an activator of cystathionine β-synthase. Hyperhomocysteinemia, a condition that recent epidemiological studies have shown to be associated with increased risk of vascular disease, arises from disrupted homocysteine metabolism. Severe hyperhomocysteinemia is due to rare genetic defects resulting in deficiencies in cystathionine beta synthase, methylenetetrahydrofolate reductase, or in enzymes involved in methyl-B12 synthesis and homocysteine methylation. Mild hyperhomocysteinemia seen in fasting conditions is due to mild impairment in the methylation pathway (i.e. folate or B12 deficiencies or methylenetetrahydrofolate reductase thermolability). Post–methionine-load hyperhomocysteinemia may be due to heterozygous cystathionine β-synthase defect or B6 deficiency. Early studies with nonphysiological high homocysteine levels showed a variety of deleterious effects on endothelial or smooth muscle cells in culture. More recent studies with human beings and animals with mild hyperhomocysteinemia provided encouraging results in the attempt to understand the mechanism that underlies this relationship between mild elevations of plasma homocysteine and vascular disease. The studies with animal models indicated the possibility that the effect of elevated homocysteine is multifactorial, affecting both the vascular wall structure and the blood coagulation system.
TRANSGENIC MODELS OF GROWTH HORMONE ACTION
Authors: Kopchick John J. , Bellush Linda L. , Coschigano Karen T.
Published: July 2002

▪ Abstract  A growth-promoting principle of the pituitary gland was discovered in 1921, and bovine growth hormone (GH) was isolated in 1944. Since then, the structure of GH as it relates to its biological activities has been an exciting research topic. Equally fascinating is the relationship between GH structure and its metabolic activities. In attempts to define some of these activities, several investigators have used GH transgenic mice as models. In this review we summarize what is known about the molecular mechanisms of GH action. We then describe some of the GH transgenic models and point out potential targets for nutrition research.
CYCLINS AND CELL CYCLE CHECKPOINTS
Authors: Johnson D. G. , Walker C. L.
Published: July 2002

▪ Abstract  The eucaryotic cell cycle is regulated by the periodic synthesis and destruction of cyclins that associate with and activate cyclin-dependent kinases. Cyclin-dependent kinase inhibitors, such as p21 and p16, also play important roles in cell cycle control by coordinating internal and external signals and impeding proliferation at several key checkpoints. Understanding how these proteins interact to regulate the cell cycle has become increasingly important to researchers and clinicians with the discovery that many of the genes that encode cell cycle regulatory activities are targets for alterations that underlie the development of cancer. Several therapeutic agents, such as DNA-damaging drugs, microtubule inhibitors, antimetabolites, and topoisomerase inhibitors, take advantage of this disruption in normal cell cycle regulation to target checkpoint controls and ultimately induce growth arrest or apoptosis of neoplastic cells. Other therapeutic drugs being developed, such as UCN-01, specifically inhibit cell cycle regulatory proteins.
STRUCTURAL DIVERSITY IN SOLID STATE CHEMISTRY:A Story of Squares and Triangles
Authors: Lee Stephen
Published: July 2002

▪ Abstract  A simple method for calculating the electronic energy of extended solids is discussed in this review. This method is based on the Hückel or tight-binding theory in which an explicit pairwise repulsion is added to the generally attractive forces of the partially filled valence electron bands. An expansion based on the power moments of the electronic density of states is discussed, and the structural energy difference theorem is reviewed. The repulsive energy is found to vary linearly with the second power moment of the electronic density of states. These results are then used to show why there is such a diversity of structure in the solid state. The elemental structures of the main group are rationalized by the above methods. It is the third and fourth power moments (which correspond in part to triangles and squares of bonded atoms) that account for much of the elemental structures of the main group elements of the periodic table. This serves as an introduction to further rationalizations of transition for noble metal alloy, binary and ternary telluride and selenide, and other intermetallic structures.Thus a cohesive picture of both covalent and metallic bonding is presented in this review, illustrating the importance of atomic orbitals and their overlap integrals.
Chemical Dynamics at Metal Surfaces
Authors: Tully John C.
Published: July 2002

Theoretical aspects of dynamical processes at metal surfaces are reviewed. Experimental challenges to theory are presented and progress toward meeting these challenges is appraised. Topics include adsorbate vibrational energy flow, inelastic molecule-surface scattering, adsorption, transient mobility, dissociation, desorption, photochemistry, and electron-induced chemistry at metal surfaces. Experimental examples cited illustrate the richness of dynamical phenomena to be understood and the necessity of developing multidimensional, beyond Born-Oppenheimer, formulations of adsorbate dynamics. Classical mechanical and quantum mechanical treatments of dynamics are contrasted. The importance of including phonon and electron-hole pair dissipation in theories of adsorbate dynamics is emphasized, and strategies for doing this in classical and quantum treatments are presented.
Delayed Ionization and Fragmentation en Route to Thermionic Emission: Statistics and Dynamics
Authors: Campbell E. E. B. , Levine R. D.
Published: July 2002

Thermionic emission is discussed as a long time (microseconds) decay mode of energy-rich large molecules, metallic and metcar clusters, and fullerenes. We review what is known and consider the many experiments, systems, and theoretical and computational studies that still need to be done. We conclude with a wish list for future work. Particular attention is given to the experimental signatures, such as the dependence on the mode of energy acquisition, and theoretical indications of a not-quite-statistical delayed ionization and to the competition of electron emission with other decay modes, such as fragmentation or radiative cooling. Coupling of the electronic and nuclear modes can be a bottleneck and quite long time-delayed ionization can be observed, as in the decay of high Rydberg states probed by ZEKE spectroscopy, before the onset of complete energy partitioning.
Cytoplasmic Signaling Pathways That Regulate Cardiac Hypertrophy
Authors: Molkentin Jeffery D , Dorn II Gerald W
Published: July 2002

▪ Abstract  This review discusses the rapidly progressing field of cardiomyocyte signal transduction and the regulation of the hypertrophic response. When stimulated by a wide array of neurohumoral factors or when faced with an increase in ventricular-wall tension, individual cardiomyocytes undergo hypertrophic growth as an adaptive response. However, sustained cardiac hypertrophy is a leading predictor of future heart failure. A growing number of intracellular signaling pathways have been characterized as important transducers of the hypertrophic response, including specific G protein isoforms, low-molecular-weight GTPases (Ras, RhoA, and Rac), mitogen-activated protein kinase cascades, protein kinase C, calcineurin, gp130-signal transducer and activator of transcription, insulin-like growth factor I receptor pathway, fibroblast growth factor and transforming growth factor β receptor pathways, and many others. Each of these signaling pathways has been implicated as a hypertrophic transducer, which collectively suggests an emerging paradigm whereby multiple pathways operate in concert to orchestrate a hypertrophic response
Chloride Channels in the Loop of Henle
Authors: Reeves W Brian , Winters Christopher J , Andreoli Thomas E
Published: July 2002

▪ Abstract  Cl− transport in the loop of Henle is responsible for reclamation of 25–40% of the filtered NaCl load and for the formation of dilute urine. Our understanding of the physiologic and molecular mechanisms responsible for Cl− reabsorption in both the thin ascending limb and thick ascending limb of Henle's loop has increased greatly over the last decade. Plasma membrane Cl− channels are known to play an integral role in transcellular Cl− transport in both the thin and thick ascending limbs. This review focuses on the functional characteristics and molecular identities of these Cl− channels, as well as the role of these channels in the pathophysiology of disease.
Specific Ca2+ Signaling Evoked by Cholecystokinin and Acetylcholine: The Roles of NAADP, cADPR, and IP3
Authors: Cancela Jose Manuel
Published: July 2002

▪ Abstract  In order to control cell functions, hormones and neurotransmitters generate an amazing diversity of Ca2+ signals such as local and global Ca2+ elevations and also Ca2+ oscillations. In pancreatic acinar cells, cholecystokinin (CCK) stimulates secretion of digestive enzyme and promotes cell growth, whereas acetylcholine (ACh) essentially triggers enzyme secretion. Pancreatic acinar cells are a classic model for the study of CCK- and ACh-evoked specific Ca2+ signals. In addition to inositol 1,4,5 trisphosphate (IP3), recent studies have shown that cyclic ADPribose (cADPr) and nicotinic acid adenine dinucleotide phosphate (NAADP) release Ca2+ in pancreatic acinar cells. Moreover, it has also been shown that both ACh and CCK trigger Ca2+ spikes by co-activation of IP3 and ryanodine receptors but by different means. ACh uses IP3 and Ca2+, whereas CCK uses cADPr and NAADP. In addition, CCK activates phospholipase A2 and D. The concept emerging from these studies is that agonist-specific Ca2+ signals in a single target cell are generated by combination of different intracellular messengers.
PROGRAMMED CELL DEATH IN PLANT DISEASE: The Purpose and Promise of Cellular Suicide
Authors: Gilchrist D. G.
Published: July 2002

▪ Abstract  The interaction of pathogens with plants leads to a disruption in cellular homeostasis, often leading to cell death, in both compatible and incompatible relationships. The mechanistic basis of this cellular disruption and consequent death is complex and poorly characterized, but it is established that host responses to pathogens are dependent on gene expression, involve signal transduction, and require energy. Recent data suggest that in animals, a genetically regulated, signal transduction–dependent programmed cell death process, commonly referred to as apoptosis, is conserved over a wide range of phyla. The basic function of apoptosis is to direct the selective elimination of certain cells during development, but it also is a master template that is involved in host responses to many pathogens. Programmed cell death in plants, while widely observed, has not been studied extensively at either the biochemical or genetic level. Current data suggest that activation or suppression of programmed cell death may underlie diseases in plants as it does in animals. This review describes some of the fundamental characteristics of apoptosis in animals and points to a number of connections to programmed cell death in plants that may lead to both a better understanding of disease processes and novel strategies for engineering disease resistance in plants.
Religion and Comparative Politics
Authors: Gill Anthony
Published: July 2002

Although scholars tend to downplay the role of religion in political life, the vast majority of people in the world profess a strong allegiance to some spiritual faith. Secularization theory has long held that religion would become irrelevant, leading many comparative scholars to ignore this potentially significant variable. A recent resurgence in religious fundamentalism and “new religious politics” has led more scholars to consider religious actors as important. However, research in this area befalls many of the same problems inherent in earlier secularization theories. A new body of scholarship, known as the “religious economy” school, seeks to address these problems by developing theories built on solid microlevel foundations of human behavior. This line of research holds great promise for the study of religion in comparative politics.
THEORETICAL FOUNDATIONS OF COGNITIVE-BEHAVIOR THERAPY FOR ANXIETY AND DEPRESSION
Authors: Brewin Chris R.
Published: July 2002

▪ Abstract  Cognitive-behavior therapy (CBT) involves a highly diverse set of terms and procedures. In this review, the origins of CBT are briefly considered, and an integrative theoretical framework is proposed that (a) distinguishes therapy interventions targeted at circumscribed disorders from those targeted at generalized disorders and (b) distinguishes interventions aimed at modifying conscious beliefs and representations from those aimed at modifying unconscious representations in memory. Interventions aimed at altering consciously accessible beliefs are related to their theoretical bases in appraisal theories of emotion and cognitive theories of emotion and motivation. Interventions aimed at modifying unconscious representations are related to their theoretical bases in learning theory and findings from experimental cognitive psychology. In the review, different formulations of CBT for anxiety disorders and depression are analyzed in terms of this framework, and theoretical issues relating to self-representations in memory and to emotional processing are considered.
Gender Inequality and Higher Education
Authors: Jacobs Jerry A.
Published: July 2002

This paper reviews a diverse literature on gender and higher education. Gender inequality is more pronounced in some aspects of the educational systems than in others. The analysis distinguishes 1) access to higher education; 2) college experiences; and 3) postcollegiate outcomes. Women fare relatively well in the area of access, less well in terms of the college experience, and are particularly disadvantaged with respect to the outcomes of schooling. Explanations of gender inequality in higher education should distinguish between these different aspects of education and should explain those contexts in which women have attained parity as well as those in which they continue to lag behind men.
The Family Responsive Workplace
Authors: Glass Jennifer L. , Estes Sarah Beth
Published: July 2002

Women's entrance into the labor market in large numbers has exacerbated incompatibilities between employer and family interests. Research reveals that conflict between paid work and family responsibilities has been linked to decreased employee productivity as well as decreased family functioning. In this review, we explore the nature of job/family incompatibility, organizational interests in family responsive policies, and the current prevalence of various policies within work organizations. We then review what is known about the effectiveness of particular family-responsive policies on organizational and family functioning. Finally, we consider barriers to further institutionalization of family responsive policy and suggest future research and policy directions.
Alcohol, Drugs, and Violence
Authors: Parker Robert Nash , Auerhahn Kathleen
Published: July 2002

A review of the scientific literature on the relationship between alcohol and violence and that between drugs and violence is presented. A review and analysis of three major theoretical approaches to understanding these relationships are also presented. A number of conclusions are reached on the basis of these efforts. First, despite a number of published statements to the contrary, we find no significant evidence suggesting that drug use is associated with violence. Second, there is substantial evidence to suggest that alcohol use is significantly associated with violence of all kinds. Third, recent theoretical efforts reviewed here have, despite shortcomings, led to significant new understanding of how and why alcohol and drugs are related to violence. Fourth, these theoretical models and a growing number of empirical studies demonstrate the importance of social context for understanding violence and the ways in which alcohol and drugs are related to violence. Fifth, the shortcomings of these theoretical models and the lack of definitive empirical tests of these perspectives point to the major directions where future research on the relationship between alcohol and violence, and between drugs and violence, is needed.
Religious Nationalism and the Problem of Collective Representation
Authors: Friedland Roger
Published: July 2002

▪ Abstract  I first argue that religion partakes of the symbolic order of the nation-state and that contemporary nationalisms are suffused with the religious. I then suggest that religious nationalism calls into question the theoretical duality of the social and the cultural, a divide variously identified with the material and the symbolic, class and status, economy and civil society. Religious nationalism, I suggest, requires an institutional approach to the project of collective representation. Religious nationalism offers a particular ontology of power, an ontology revealed and affirmed through its politicized practices and the central object of its political concern, practices that locate collective solidarity in religious faith shared by embodied families, not in contract and consent enacted by abstract individual citizens. Understanding the institutional basis of religious nationalist discourse allows us to understand its affinities with socialist politics. If religious nationalism derives from religion's institutional heterology with the capitalist market and the democratic state, then it suggests the limits of a social theory that occludes that heterology. In the remainder of the paper, I argue that religious nationalism cannot be adequately understood either through Pierre Bourdieu's theory of habitus and field, nor through Jeffrey Alexander's theory of civil society. Bourdieu's theory of fields imports the logic of dominant institutions and thereby culturally homogenizes the institutional diversity of contemporary society, making the stake of politics a culturally empty space of domination. Alexander's theory of civil society, while rich in cultural substance, identifies civil society with democratic political culture and thereby makes unnecessarily restrictive assumptions about the institutional sources of collective representation in modern society.
Making Connections: A Model for On-Line Interaction
Authors: Metros Susan E.
Published: July 2002

The overuse of visual imagery and the redundancy of information in traditional and new communication media have desensitized our society, resulting in an emotional bankruptcy. The World Wide Web communication medium, with its highly visual interface and virtual environments, perpetuates and aggravates this situation. The “new designers” of the twenty-first century must partner with technology experts, content specialists and common users to reinvigorate imagination and rekindle emotions. To this end, we can identify and extract the six essential ingredients of engagement from the traditional performing arts, communication and design theory and recast them to support new media that are both visually stimulating and emotionally provocative.
Concord in Minimalist Theory
Authors: Carstens Vicki
Published: July 2002

Concord within DP argues that movement is driven by uninterpretable features of either the target or the moved item, contra Chomsky 1995. The uninterpretable f-features of which concord consists must be eliminated by LF, to satisfy Full Interpretation. But raising of inflected APs and KPs into checking relations with N0 cannot be motivated, in Chomsky's system, since N0 has no uninterpretable features that these items can check. Assuming Kayne's (1994, 1998) proposal for APs, the problem can be partially overcome, but inflected “of” constructions still lack an account. Chomsky's (1998) probe-goal approach applied to concord also encounters difficulties, avoided under revision of the (1995) system: if the f-features of APs and KPs drive them to raise for checking, correct results are obtained.
Improving Accuracy in Word Class Tagging through the Combination of Machine Learning Systems
Authors: Halteren Hans van , Zavrel Jakub , Daelemans Walter
Published: July 2002

We examine how differences in language models, learned by different data-driven systems performing the same NLP task, can be exploited to yield a higher accuracy than the best individual system. We do this by means of experiments involving the task of morphosyntactic word class tagging, on the basis of three different tagged corpora. Four well-known tagger generators (hidden Markov model, memory-based, transformation rules, and maximum entropy) are trained on the same corpus data. After comparison, their outputs are combined using several voting strategies and second-stage classifiers. All combination taggers outperform their best component. The reduction in error rate varies with the material in question, but can be as high as 24.3% with the LOB corpus.
Visuospatial Attention Shift and Motor Responses in Cerebellar Disorders
Authors: Yamaguchi Shuhei , Tsuchiya Haruhisa , Kobayashi Shotai
Published: July 2002

The cerebellum has been implicated in higher cognitive functions including learning, memory, and attention as well as its well-known role in motor programming. Recent studies have suggested that the cerebellum plays a role in shifts of attention. We investigated the contribution of the cerebellum to visuospatial attentional ability in a trial-by-trial cueing task involving the covert orienting of spatial attention. We recorded event-related evoked potentials (ERPs) and reaction times (RTs) in patients with cerebellar degenerative disorders affecting mainly the lateral cerebellum and compared them to age-matched controls. The RT data demonstrated that both the cerebellar patients and control subjects responded to the valid cues faster than to the invalid cues for both the central and the peripheral cues. Consistent with the RT data, the ERP data showed a comparable generation of attention shift-related negativities during the cue-target interval for both the central and the peripheral cue experiments. The early negative component of the ERP to the target was also comparably modulated in both groups as a function of cue validity, suggesting efficient facilitation of sensory pathways by prior allocation of spatial attention to the cued place. Conversely, the late negative deflection preceding the imperative target stimulus and the late sustained positivity following target presentation, which reflect neural activities for response preparation and selection, were reduced in the cerebellar group. These findings suggest that the lateral cerebellum makes little contribution to visuospatial attention shift in either the voluntary or automatic modes and support a role of the lateral cerebellum in the neural system required for response preparation and selection.
Patterns of Brain Activity during Visual Imagery of Letters
Authors: Raij Tommi
Published: July 2002

Cortical signals associated with visual imagery of letters were recorded from 10 healthy adults with a whole-scalp 122-channel neuromagnetometer. The auditory stimulus sequence consisted of 20 different phonemes corresponding to single letters of the Roman alphabet and of tone pips (17%), delivered once every 1.5 sec in a random order. The subjects were instructed to visually imagine the letter corresponding to the auditory stimulus and to examine its visuospatial properties: The associated brain activity was compared with activity evoked by the same stimuli when the subjects just detected the intervening tones. All subjects produced broad imagery-related responses over multiple cortical regions. After initial activation of the auditory cortices, the earliest imagery-related responses originated in the left prerolandic area 320 msec after the voice onset. They were followed within 70 msec by signals originating in the posterior parietal lobe close to midline (precuneus) and, 100 msec later, in the posterior superior temporal areas, predominantly in the left hemisphere. The activations were sustained and partially overlapping in time. Imagery-related activity in the left lateral occipital cortex was observed in two subjects, and weak late activity in the calcarine cortex in one subject. Real audiovisually presented letters activated multiple brain regions, and task-induced visuospatial processing of these stimuli further increased activity in some of these regions and activated additional areas: Some of these areas were activated during imagery as well. The results suggest that certain brain areas involved in high-level visual perception are activated during visual imagery and that the extent of imagery-related activity is dictated by the requirements of the stimuli and the task.
Semantic Integration in Sentences and Discourse: Evidence from the N400
Authors: Berkum Jos J. A. van , Hagoort Peter , Brown Colin M.
Published: July 2002

In two ERP experiments we investigated how and when the language comprehension system relates an incoming word to semantic representations of an unfolding local sentence and a wider discourse. In Experiment 1, subjects were presented with short stories. The last sentence of these stories occasionally contained a critical word that, although acceptable in the local sentence context, was semantically anomalous with respect to the wider discourse (e.g., Jane told the brother that he was exceptionally slow in a discourse context where he had in fact been very quick). Relative to coherent control words (e.g., quick), these discourse-dependent semantic anomalies elicited a large N400 effect that began at about 200 to 250 msec after word onset. In Experiment 2, the same sentences were presented without their original story context.

Although the words that had previously been anomalous in discourse still elicited a slightly larger average N400 than the coherent words, the resulting N400 effect was much reduced, showing that the large effect observed in stories depended on the wider discourse. In the same experiment, single sentences that contained a clear local semantic anomaly elicited a standard sentence-dependent N400 effect (e.g., Kutas & Hillyard, 1980). The N400 effects elicited in discourse and in single sentences had the same time course, overall morphology, and scalp distribution. We argue that these findings are most compatible with models of language processing in which there is no fundamental distinction between the integration of a word in its local (sentence-level) and its global (discourse-level) semantic context.
Stationary and Integrated Autoregressive Neural Network Processes
Authors: Trapletti Adrian , Leisch Friedrich , Hornik Kurt
Published: July 2002

We consider autoregressive neural network (AR-NN) processes driven by additive noise and demonstrate that the characteristic roots of the shortcuts—the standard conditions from linear time-series analysis—determine the stochastic behavior of the overall AR-NN process. If all the characteristic roots are outside the unit circle, then the process is ergodic and stationary. If at least one characteristic root lies inside the unit circle, then the process is transient. AR-NN processes with characteristic roots lying on the unit circle exhibit either ergodic, random walk, or transient behavior. We also analyze the class of integrated AR-NN (ARI-NN) processes and show that a standardized ARI-NN process “converges” to a Wiener process. Finally, least-squares estimation (training) of the stationary models and testing for nonstationarity is discussed. The estimators are shown to be consistent, and expressions on the limiting distributions are given.
Attractor Dynamics in Feedforward Neural Networks
Authors: Saul Lawrence K. , Jordan Michael I.
Published: July 2002

We study the probabilistic generative models parameterized by feedfor-ward neural networks. An attractor dynamics for probabilistic inference in these models is derived from a mean field approximation for large, layered sigmoidal networks. Fixed points of the dynamics correspond to solutions of the mean field equations, which relate the statistics of each unittothoseofits Markovblanket. We establish global convergence of the dynamics by providing a Lyapunov function and show that the dynamics generate the signals required for unsupervised learning. Our results for feedforward networks provide a counterpart to those of Cohen-Grossberg and Hopfield for symmetric networks.