bluuebunny/crossref_metadata_2025 huggingface dataset:
INFLUENCE OF MECHANICAL STRESS ON EXTRACELLULAR MATRIXES SYNTHESIZED BY CHONDROCYTES SEEDED ONTO ALGINATE AND HYALURONATE-BASED 3D BIOSYSTEMS
Authors: GIGANT-HUSELSTEIN C. , DUMAS D. , HUBERT P. , BAPTISTE D. , DELLACHERIE E. , MAINARD D. , NETTER P. , PAYAN E. , STOLTZ J. F.
Published: June 2003

Articular cartilage is an hydrated tissue that withstands and distributes mechanical stresses. The chondrocytes respond to mechanical signals by regulating their metabolic activity through complex biological and biophysical interactions with the extracellular matrix (ECM). The objective of this work was to compare, under mechanical stress, the ECMs synthesized by rat chondrocytes seeded onto biosystems based on alginate (Alg), hyaluronic acid (HA) and a HA amphiphilic derivative. The mechanical stress simulates the traumatisms resulting from accidental shocks or intensive physical exercise by knocking the biosystems together. The investigation of ECMs neosynthesized by chondrocytes was carried out according to various criteria: proliferation, proteoglycans synthesis activity, expression of type I and type II collagens and the expression of α5/β1 integrin.

The results obtained for the stress applied on neosynthesized matrixes of 3, 10, 17 and 24 days evidenced a high proliferation and proteoglycans synthesis activity for cells submitted to a knocking process. For all biosystems, the neosynthesized matrix contained an important level of collagen, which was in part of type II, whatever the biosystems.

Finally, the chemical modification of HA by long hydrophobic alkyl chains, affords an amphiphilic derivative with viscoelastic properties perfectly mimicking those of matricial environment of chondrocytes. This study showed that the HA amphiphilic derivative induced biological effects similar to those of parent HA containing no hydrophobic modifications.
IMPACTS OF THE ECONOMIC TRANSITION ON ENVIRONMENTAL REGULATION IN CHINA
Authors: MAO WENFENG , ZHANG SHUJUAN
Published: June 2003

Economic transition has significant implications for environmental regulation; however, the linkages between them have received little attention in the research literature or in governmental studies until very recently. The paper examines the impacts of economic transition on environmental regulation in China. It first reviews the normative and structural features of China's economic transition. It then analyzes their broad impacts on environmental regulation in China in terms of environmental regulatory instruments losing effectiveness, intervention by local governments, trans-boundary environmental problems, conflict of interests for environmental regulators, massive resistance from the regulated, and some positive impacts. It finally draws prospects for environmental regulation in China in the context of further economic transition. The paper argues that the economic transition in China has produced mixed impacts on its environmental regulation, and that the future prospects for environmental regulation under further economic transition are also mixed.
AN ASSESSMENT OF THE ROLE OF ENVIRONMENTAL REPORTING IN SUPPORTING SHARE VALUES IN FTSE100 COMPANIES
Authors: WALMSLEY JAMES DANIEL , BOND ALAN
Published: June 2003

This paper explores the relationship between corporate environmental reporting and share price performance amongst companies in two industry groups listed on the UK FTSE (Financial Times Stock Exchange) 100 as of the 30th July 2001. The hypothesis tested is that the production of good quality corporate environmental reports (CERs) benefits company share price, by demonstrating to investors an awareness of risk, liability, legislation and opportunities as well as providing a collection of policy, impacts, temporal trends, targets and commitment.

Some other studies in this area have concluded that a positive relationship exists between corporate environmental management and performance (including environmental reporting) and share value. The results of this paper differ however, and show that on average, the production of environmental reports by FTSE100 companies (in the energy and utilities and financial services sectors) has not lead to improved historical share price performance when compared to non-reporting companies, although there is strong evidence for reduced volatility of share price. Results for sector performance varied from those obtained from individual company level. The two companies assessed as producing the best reports in their industry sector outperformed both the FTSE100 benchmark, and many of their competitors for the five-year period studied.

Whilst there are many benefits to be gained by listed companies through environmental reporting, such as enhancing image and improving public and investor opinion, a positive attitude to the environment, as demonstrated through environmental reporting, can provide an indication of a truly strategic approach to business. Yet there are so many factors involved, it is not possible from the results to conclude that environmental reporting supports share value.
The RR Lyrae Stars
Authors: Preston George W.
Published: July 2003

For more than fifty years the RR Lyrae stars have played a prominent role in problems of galactic structure, first as distance indicators and more recently as population indicators. This has followed from the apparent homogeneity of the group, the large number present in the Galaxy, and their moderately high luminosities, which render them visible at large distances. However, in the past decade it has become clear that RR Lyrae stars are heterogeneous in many observable parameters. This heterogeneity limits their usefulness in some contexts and enhances their value in others. In addition to their applications in galactic research, the RR Lyrae stars are of current astrophysical interest on account of the line-doubling and emission that occur during rising light, the multiple periodicities found in many of them, and various other phase- and period-dependent phenomena that bear on the theory of stellar pulsation. In this review we summarize recent developments in these areas.
The Dynamics of Star Clusters
Authors: Michie Richard W.
Published: July 2003

The dynamics of star clusters is here discussed from a viewpoint that includes their formation, evolution, present structure, and eventual fate. The aim is to present a basic understanding of the physical principles, the emphasis being on the implications of the long free path of the average stars. Some topics are the internal interactions between cluster stars, the consequences of loss of mass and angular momentum, the interaction with the galaxy and interstellar clouds, and the development of the currently observed luminosity functions. It is stressed in this article that the present structure of star clusters reflects to some extent the process of fragmentation into stars in the gas clouds from which the clusters formed. Thus one major purpose of this article is to remove the consideration of star clusters from the confines of the isolated stationary structure problem and to turn attention to the origin and evolution of these small and intermediate-sized stellar systems.
Spectra of Comets and Their Interpretation
Authors: Arpigny Claude
Published: July 2003

Important progress has been made in the study of cometary spectra in recent years thanks to the introduction of high resolution. Spectra of comets have been taken with the coudé spectrographs of large telescopes. Thus the precision of the wavelength measurements has been increased appreciably, new emission lines have been discovered, some of which have been identified, and the analysis of the detailed structure of molecular bands has become possible. Similarly, some information has been derived concerning the kinematical and the spatial structure of comets' heads. On the theoretical side, efforts have been made to take advantage of the higher quality of the new observational data, and a better interpretation of these data has been obtained in some cases. It is not the purpose of the present review to give a complete description of the observational material now available, especially since such a description can be found in a recent .article by Swings (1). Rather shall we emphasize the theoretical aspects of the study of the spectra of comets and present a critical discussion of recent investigations regarding the details of the production of the cometary light
Blue Stragglers and Other Stellar Anomalies: Implications for the Dynamics of Globular Clusters
Authors: Bailyn Charles D.
Published: July 2003

There are several observed phenomena in globular clusters that are thought to be the result of dynamical processes or binary star evolution. This review examines these manifestations of the interaction between globular cluster dynamics and stellar evolution. Blue stragglers may be formed by the evolution of primordial binaries or by collisions. Current evidence suggests that both processes are likely to occur, and that the observed blue straggler sequences can place dynamically interesting limits on rates. Color gradients in globular clusters are thought to be caused by the stripping of giants by collisions, although the creation of blue subdwarfs by the same process may also be required to explain the observations. The observed X-ray sources and radio pulsars are apparently also made by a variety of dynamical processes that are still not fully understood.
Intraday Variability in Quasars and BL LAC Objects
Authors: Wagner S. J. , Witzel A.
Published: July 2003

Active galactic nuclei with flat radio spectra exhibit significant variations of continuum flux density on time scales of days or less throughout the entire wavelength range. These rapid variations tightly constrain the diameters of the emitting regions and imply extremely high photon densities if the variations are intrinsic. At radio frequencies the flux densities of compact objects may flicker due to interstellar scintillation, and in all frequency bands microlensing by stars in in­tervening galaxies may introduce variations that are not intrinsic to the source. We review the characteristics of these variations in the various electromagnetic bands. Extrinsic mechanisms may affect the light curves of compact extragalactic sources, but close correlations between flares recorded in different bands strongly support the assumption that intraday variability is an intrinsic phenomenon.

The apparent brightness temperatures in the radio regime exceed 1017 K and imply relativistic beaming with very high Doppler factors, coherent radiation mechanisms, or special geometric effects.
High-Energy Particles in Solar Flares
Authors: Hudson H. , Ryan J.
Published: July 2003

Accelerated particles appear to coexist inseparably with most forms of energy release in solar flares and coronal mass ejections. We identify at least five different populations of high-energy electrons and ions. High-energy particles, accelerated efficiently in the flare in great numbers, transport a large fraction of the flare energy to other sites. This behavior makes them an integral part of the flare process. Much new data has come from two spacecraft launched in 1991: the Compton Gamma­Ray Observatory and Yohkoh. This review concentrates on particles in flares, mainly using X-ray and gamma-ray data rather than measurements of “escaping” particles observed in interplanetary space.
The Old Open Clusters of the Milky Way
Authors: Friel E. D.
Published: July 2003

The Galactic open clusters, in particular the oldest members, serve as excellent probes of the structure and evolution of the Galactic disk. Individual clusters provide excellent tests of stellar and dynamical evolution. Cluster spatial and age distributions provide insight into the processes of cluster formation and destruction that have allowed substantial numbers of old open clusters to survive. Spectroscopic and photometric data for the old clusters yield kinematic, abundance, and age information that clarifies the relationship between the old open cluster population and other Galactic populations. New samples of old open clusters, which span a large range in distance and age, are used to define disk abundance gradients and the cluster age-metallicity relationship, and they point to a complex history of chemical enrichment and mixing in the disk.
Gamma-Ray Bursts
Authors: Fishman Gerald J. , Meegan Charles A.
Published: July 2003

The present status of gamma-ray burst research is reviewed, with an emphasis on recent observations of their temporal, spectral, and global distribution properties. The observed sky distribution of weak gamma-ray bursts constrains the allowable geometrical models to sources in either a giant spherical galactic halo or to sources at cosmological distances. Observations of time dilation consistent with the latter have been reported. Extensive searches for a counterpart to gamma-ray bursts in other wavelength regions have thus far proved negative. In spite of the abundance of new observations of gamma-ray bursts, their energy source and emission mechanism remain highly speculative. New, rapid counterpart search efforts and several new space-borne experiments may provide the needed observations to make progress in the field
The Solar Neutrino Problem
Authors: Haxton W. C.
Published: July 2003

The solar neutrino problem has persisted for almost three decades. Recent results from Kamiokande, SAGE, and GALLEX indicate a pattern of neutrino fluxes that is very difficult to reconcile with plausible variations in standard solar models. This situation is reviewed, and suggested particle physics solutions are discussed. A summary is given of the important physics expected from SNO, SuperKamiokande, and other future experiments.
The First Twenty Years
Authors: Siegel Bernard J.
Published: July 2003

After twenty years as founder and editor of the Annual Review of Anthropology (ARA) I have been requested by the Editorial Committee to ponder the developments in the several subfields of anthropology over this period of time, as reflected in the topics selected for review in this enterprise. Where I feel some competence to do so, I shall offer a critique of where we have come from and where we might be going. Before entering into the fray, I will provide some history of the ARA and a brief account of my background, both of which affect the structure and the content of these volumes. I am pleased to report that the new editor is William Durham, a distinguished biological anthropologist whose research interests lie in the interface between biological and cultural evolution.
Consumption and Commodities
Authors: Miller D.
Published: July 2003

This review contends that the study of consumption and commodities represents a major transformation in the discipline of anthropology. It documents this metamorphosis by examining how the debate on gifts and commodities transcended its original formulation as good versus evil. It then examines the recent growth and maturity of material culture studies and nascent developments that may give rise to a political economy of consumption. It notes, however, that there is still a paucity of ethnographic research specifically devoted to these topics. The review concludes by arguing that the study of consumptiona nd commoditiesis particularly close to traditions established in the study of kinship and it may come to replace kinship as the core of anthropology, even though the two topics often have been viewed as antithetical.
Biological Changes in Human Populations with Agriculture
Authors: Larsen Clark Spencer
Published: July 2003

Agriculture has long been regarded as an improvement in the human condition: Once Homo sapiens made the transition from foraging to farming in the Neolithic, health and nutrition improved, longevity increased, and work load declined. Recent study of archaeological human remains worldwide by biological anthropologists has shown this characterization of the shift from hunting and gathering to agriculture to be incorrect. Contrary to earlier models, the adoption of agriculture involved an overall decline in oral and general health. This decline is indicated by elevated prevalence of various skeletal and dental pathological conditions and alterations in skeletal and dental growth patterns in prehistoric farmers compared with foragers. In addition, changes in food composition and preparation technology contributed to craniofacial and dental alterations, and activity levels and mobility decline resulted in a general decrease in skeletal robusticity. These findings indicate that the shift from food collection to food production occasioned significant and widespread biological changes in human populations during the last 10,000 years.
Toward A Life History of the Hominidae
Authors: Smith B. Holly , Tompkins Robert L.
Published: July 2003

Two new developments promise to greatly improve our ability to reconstruct the evolution of the human life cycle: 1. the introduction of the comparative methodology of life history into anthropology and 2. research on bone and dental development that reveals a world of life history preserved in the fossil record. Comparative study suggests that the human strategy depends on rich energy sources and low mortality and that our general rate of growth and aging evolved in parallel with brain size. It now appears that the australopithecines were a substantially primitive grade of hominid with life histories more like apes than humans. The life cycle of early Homo erectus was probably unlike any living hominoid: Evidence suggests that it grew up somewhat faster than living humans, it lacked an adolescent growth spurt, and H. erectus infants were more helpless than those of chimpanzees (but conceivably of more mature body proportion and motor advancement than our own). The appearance of fully modern life histories is still not fully resolved: Early Pleistocene Homo probably did not share them, and late Pleistocene hominids probably did, but life history is still little documented in the intervening million years. Although many details remain to be uncovered, the combination of advancing method and theory should soon lead to more robust models of human origins.
My Early Experiences in the Study of Foods and Nutrition
Authors: McCollum E. V.
Published: July 2003

This chapter was written at the request of the Editorial Committee. Among the suggestions which the Editor offered as to the kind of chapter which would be acceptable was one to the effect that the writer might prepare “... an autobiographical sketch in which he describes his own experiences as a student, a teacher, and an investigator.” It is this suggestion that has been folIowed. These reminiscences will be limited to my educational experiences and to the decade of 1907 to 1917, the period of my earliest experiences as a nutrition investigator. This was a decade of special importance for clarifying the ideas of workers in this field as to how to use animals effectively for discovering the existence of hitherto unsuspected nutrients, a task for which chemical procedures alone were inadequate. It was the decade when the initial successes were achieved in determining, in individual naturally occurring food substances, and in some mixtures of foods, the nature of the chemical deficiencies which limited their ability to support physiological well-being in an animal.
FROM BACTERIAL NUTRITION TO ENZYME STRUCTURE: A Personal Odyssey
Authors: Snell Esmond E.
Published: July 2003

As a former editor or member of the Editorial Board of the Annual Review of Biochemistry I helped to select authors of the prefatory chapters for more than 20 years. Now I am asked to write one myself. The first such chapter appeared in 1953 with the prefatorial statement: “This is the first of a series in which it is the hope of the Editorial Committee that our elders in biochemistry will give us through chapters of a historical and philosophical character the benefit of their long years of experience in biochemistry.” With one exception, the chapters have appeared regularly ever since. Their authors comprise a group I am proud to join even while harboring some doubts about really belonging. Their autobiographical accounts have added much to our understanding of how and why they became biochemists, and how biochemistry itself developed. I shall continue in this tradition.
TRIPLEX DNA STRUCTURES
Authors: Frank-Kamenetskii Maxim D. , Mirkin Sergei M.
Published: July 2003

A DNA triplex is formed when pyrimidine or purine bases occupy the major groove of the DNA double Helix forming Hoogsteen pairs with purines of the Watson-Crick basepairs. Intermolecular triplexes are formed between triplex forming oligonucleotides (TFO) and target sequences on duplex DNA. Intramolecular triplexes are the major elements of H-DNAs, unusual DNA structures, which are formed in homopurine-homopyrimidine regions of supercoiled DNAs. TFOs are promising gene-drugs, which can be used in an anti-gene strategy, that attempt to modulate gene activity in vivo. Numerous chemical modifications of TFO are known. In peptide nucleic acid (PNA), the sugarphosphate backbone is replaced with a protein-like backbone. PNAs form P-loops while interacting with duplex DNA fonning triplex with one of DNA strands leaving the other strand displaced. Very unusual recombination or parallel triplexes, or R-DNA, have been assumed to form under RecA protein in the course of homologous recombination.
SELECTIN-CARBOHYDRATE INTERACTIONS AND THE INITIATION OF THE INFLAMMATORY RESPONSE
Authors: Lasky Laurence A.
Published: July 2003

The orderly migration of various white blood cell types to inflammatory sites is a highly regulated process that involves a diversity of adhesion and signaling molecules. This cellular influx is initiated by relatively low affinity interactions that allow for leukocytes to roll along the vascular surface. This rolling phenomenon is mediated by adhesive interactions between lectin containing adhesion molecules, termed selectins, on both the vascular endothelium and leukocytes, and carbohydrate ligands immobilized on mucin-like scaffolds. This adhesion allows for a rapid recognition of various cell types under the conditions of vascular flow, with the result that inflammatory cells are specifically decelerated adjacent to sites of inflammation. This review focuses on the various biochemical aspects of the interactions between the selectins and their cognate carbohydrate ligands, with an emphasis on the importance of these adhesive events to the inflammatory response.
DNA PROCESSING REACTIONS IN BACTERIAL CONJUGATION
Authors: Lanka Erich , Wilkins Brian M.
Published: July 2003

Bacterial conjugation is an important source of genetic plasticity. The initiation complex for conjugative transfer of transmissible plasmids—the relaxosome—is a specific DNA-protein structure that has been isolated from cells and reconstituted from purified components in vitro. Complexes containing uncleaved DNA and DNA cleaved at the nicsite in the origin of transfer (oriT) coexist in equilibrium. Relaxase is usually loaded onto oriT by accessory DNA-binding proteins. Relaxase catalyzes cleavage of a specific phosphodiester bond at nic and becomes covalently linked through a tyrosyl residue to the 5′ terminus of the cleaved strand. Cleaved DNA may be unwound for transfer by a plasmid-encoded helicase. Single-strand transfer is thought to occur by a replicative rolling circle mechanism. Termination of a round of transfer is achieved by the cleaving-joining activity of the relaxase linked to the 5′ end of the transferring strand. Relationships between DNA processing reactions and conjugative interactions of cell envelopes are particularly obscure aspects of the conjugation cycle.
RELATIONSHIPS BETWEEN DNA REPAIR AND TRANSCRIPTION
Authors: Friedberg Errol C.
Published: July 2003

Multiple relationships have been noted between DNA repair and transcription in both prokaryotic and eukaryotic cells. First, in both prokaryotes and eukaryotes nucleotide excision repair of the template strand of transcriptionally active regions of the genome is faster than in the coding strand. In prokaryotes the biochemical basis for this kinetic difference appears to be related to the specific coupling of repair to arrested transcription by RNA polymerase. The biochemical basis for strand-specific repair in eukaryotes is unknown. Second, in eukaryotes some or all of the subunits of transcription factor IIH (TFIIH) are required for nucleotide excision repair. The biological significance of this dual function of TFIIH proteins is not obvious. Finally, there are indications that the genes CSA and CSB, which are implicated in the human hereditary disease Cockayne syndrome, may have a role in transcription.
TELOMERE LENGTH REGULATION
Authors: Greider Carol W.
Published: July 2003

Telomeres are the components of chromosome ends that provide stability and allow the complete replication of the ends. Telomere length is maintained by a balance between processes that lengthen and those that shorten telomeres. Telomeraseis a ribonucleoprotein polymerase that specifically elongates telomeres. In human cells telomere length is not maintained and telomerase is not active in some tissues. In tumors, however, telomerase is active and may be required for the growth of cancer cells. Thus understanding telomerase and telomere length regulation may help us understand tumor progression. Evidence from various organisms suggests that several factors influence telomere length regulation, such as telomere binding proteins, telomere capping proteins, telomerase, and DNA replication enzymes. Understanding how these factors interact to coordinate the regulation of telomere length will allow a more complete understanding of telomere function in the cell.
CROSSTALK BETWEEN NUCLEAR AND MITOCHONDRIAL GENOMES
Authors: Poyton Robert O. , McEwen Joan E.
Published: July 2003

This review focuses on molecular mechanisms that underlie the communication between the nuclear and mitochondrial genomes in eukaryotic cells. These genomes interact in at least two ways. First, they contribute essential subunit polypeptides to important mitochondrial proteins; second, they collaborate in the synthesis and assembly of these proteins. The first type of interaction is important for the regulation of oxidative energy production. Isoforms of the nuclear-coded subunits of cytochrome c oxidase affect the catalytic functions of its mitochondrially coded subunits. These isoforms are differentially regulated by environmental and developmental signals and probably allow tissues to adjust their energy production to different energy demands. 'Ihe second type of interaction requires the bidirectional flow of information between the nucleus and the mitochondrion. Communication from the nucleus to the mitochondrion makes use of proteins that are translated in the cytosol and imported by the mitochondrion. Communication from the mitochondrion to the nucleus involves metabolic signals and one or more signal transduction pathways that function across the inner mitochondrial membrane. An understanding of both types of interaction is important for an understanding of OXPHOS diseases and aging.
Vasculogenesis
Authors: Risau Werner , Flamme Ingo
Published: July 2003

Induction by fibroblast growth factors of mesoderm during gastrulation leads to blood-forming tissue, including angioblasts and hemopoietic cells, that together constitute the blood islands of the yolk sac. The differentiation of angioblasts from mesoderm and the formation of primitive blood vessels from angioblasts at or near the site of their origin are the two distinct steps during the onset of vascularization that are defined as vasculogenesis. Vascular endothelial growth factor and its high-affinity receptor tyrosine kinase flk-1 represent a paracrine signaling system crucial for the differentiation of endothelial cells and the development of the vascular system. Specific cell adhesion molecules such as VE-cadherin and PECAM-1 (CD-31), and transcription factors such as ets-1, as well as mechanical forces and vascular regression and remodeling are involved in the subsequent events of endothelial cell differentiation, apoptosis, and angiogenesis.
Keratins and the Skin
Authors: Fuchs Elaine
Published: July 2003

Keratins are the major structural proteins of the vertebrate epidermis and its appendages, constituting up to 85% of a fully differentiated keratinocyte. Together with actin microfilaments and microtubules, keratin filaments make up the cytoskeletons of vertebrate epithelial cells. Traced as far back in the evolutionary kingdom as mollusks, keratins belong to the superfamily of intermediate filament (IF) proteins that form alpha-helical coiled-coil dimers which associate laterally and end-to-end to form 10-nm diameter filaments. The evolutionary transition between organisms bearing an exoskeleton and those with an endoskeleton seemed to cause considerable change in keratin. Keratins expanded from a single gene to a multigene family. Of the approximately 60 IF genes in the human genome, half encode keratins, and at least 18 of these are expressed in skin. Vertebrate keratins are subdivided into two sequence types (I and II) that are typically coexpressed as specific pairs with complex expression patterns. The filament-forming capacity of a pair is dependent upon its intrinsic ability to self-assemble into coiled-coil heterodimers, a feature not required of the invertebrate keratins (Weber et al 1988). Approximately 20,000 heterodimers of type I and type II keratins assemble into an IF. Mutations that perturb keratin filament assembly in vitro can cause blistering human skin disorders in vivo. From studies of these diseases, an important function of keratins has been unraveled. These filaments impart mechanical strength to a keratinocyte, without which the cell becomes fragile and prone to rupturing upon physical stress. In this review, studies on the pattern of expression, structure, and function of skin keratins are summarized, and new insights into the functions of these proteins and their involvement in human disease are postulated.
Global Mantle Tomography: Progress Status in the Past 10 Years
Authors: Romanowicz Barbara
Published: July 2003

▪ Abstract  We review the present status of global mantle tomography and discuss two main classes of models that have been developed in the past 10 years: P velocity models based on large datasets of travel times from the International Seismological Centre bulletins, often referred to as “high resolution” models, and S velocity models based on a combination of surface wave and hand picked body wave travel times, or waveforms, referred to as “long wavelength” models. We discuss their respective strengths and weaknesses, as well as progress in the resolution of other physical parameters, such as anisotropy, anelasticity, density, and bulk sound velocity using tomographic approaches. We present the view that future improvements in global seismic tomography require the utilization of the rich information contained in complete broadband seismic waveforms. This is presently within our reach owing to theoretical progress as well as the increase in computational power in recent years.
Internationalizing Nuclear Safety: The Pursuit of Collective Responsibility
Authors: Barkenbus Jack N. , Forsberg Charles
Published: July 2003

The future of nuclear energy could depend upon the international infrastructure established to ensure the creation of a strong and uniform safety culture. Deliberations during the 1990s, leading to the recently promulgated International Nuclear Safety Convention, held out the prospect of both bolstering nuclear safety and gaining public recognition of the need to address transboundary safety concerns head-on. Unfortunately, the Convention that emerged from the deliberations constitutes little more than another form of technical as::istance. The basis for an alternative, and more substantial, Convention is presented—one that would be based on the establishment and evaluation of perfonnance standards, the creation of a series of political “firebreaks,” and the encouragement of nuclear power plant designs that minimize the catastrophic offsite consequences of accidents.
Resistance to Avermectins: Extent, Mechanisms, and Management Implications
Authors: Clark J. M. , Scott J. G. , Campos F. , Bloomquist J. R.
Published: July 2003

The avermectins represent a group of natural compounds with potent pesticidal activities. Because of their novel mode of action, they represent an important resource for pest control and resistance management. In the Colorado potato beetle, the house fly, and the two-spotted spider mite, resistance to abamectin is usually autosomal, recessive, and polygenic. Although these aspects are beneficial in resistance management, the fact that resistance could be readily selected for suggests that abamectin needs to be used in moderation. Furthermore, several major resistance mechanisms (e.g. excretion, oxidative metabolism, penetration) and minor factors (e.g. altered target site, conjugation, hydrolysis/sequestration) have been implicated in abamectin resistance. Thus, the question is not whether resistance to abamectin will occur but is simply when and how it will occur. To address this problem, we have gathered information on the genetics, biochemical mechanisms, effectiveness of synergists, and cross-resistances to other insecticides from three abamectin-resistant insects. Judicious implementation of this information may prove useful in the resistance management of this natural pesticide.
Regional and Functional Differentiation in the Insect Fact Body
Authors: Haunerland N. H. , Shirk P. D.
Published: July 2003

Insect fat body historically has been considered a single tissue with multiple and diverse metabolic functions. Recent findings indicate that functionally distinct regions of fat body exist in some insects and that these regions often have unique morphologies. Regionally differentiated fat bodies in Lepidoptera have been associated with the segregation of synthetic and storage activities. The loss of biosynthetic capacity for storage proteins at the beginning of metamorphosis is the consequence of the histolysis of a larval specific histotype, whereas the histotype that accumulates storage proteins persists into the adult stage. In Diptera, functional histotypes are arranged along the anteriorposterior axis and between the larval and adult stages. Based on these models. we predict that the use of immunological and molecular probes will lead to the identification of regionally and functionally differentiated fat body histotypes in many insects.
Ecology of Insect Communities in Nontidal Wetlands
Authors: Batzer Darold P. , Wissinger Scott A.
Published: July 2003

Published research about wetland insects has proliferated, and a conceptual foundation about how wetland insect populations and communities are regulated is being built. Here we review and synthesize this new body of work. Our review begins with a summary of insect communities found in diverse wetland types, including temporary pools, seasonally flooded marshes, perennially flooded marshes, forested floodplains, and peatlands. Next, we critically discuss research on the population and community ecology of wetland insects, including the importance of colonization strategies and insect interactions with the physical environment, plants, predators, and competitors. Results from many of the experimental studies that we review indicate that some commonly held beliefs about wetland insect ecology require significant reevaluation. We then discuss the importance of wetland insect ecology for some applied concerns such as efforts to manage wetland insect resources as waterfowl food and development of ecologically sound strategies to control pest mosquitoes. We conclude with a discussion of wetland conservation, emphasizing insect aspects.
Discontinuous Gas Exchange in Insects
Authors: Lighton John R. B.
Published: July 2003

Many insects exchange respiratory gases cyclically and discontinuously. A typical discontinuous gas exchange cycle (DGC) starts with a closed-spiracle (C) phase, during which little external gas exchange takes place, followed by a fluttering-spiracle (F) phase, which is usually dominated by diffusive oxygen uptake. The DGC is terminated by an open-spiracle (O) phase, during which accumulated CO2 escapes. This review critically examines the applicability of the DGC to insect gas exchange in general, discusses the primary mechanisms of gas exchange in the F and O phases, evaluates the widespread hypothesis that the DGC lowers respiratory water loss rates adaptively, and proposes new hypotheses concerning the evolutionary genesis of the DGC in insects and other tracheate arthropods.
Geographic Structure of Insect Populations: Gene Flow, Phylogeography, and Their Uses
Authors: Roderick George K.
Published: July 2003

Geographic structure of populations is a fundamental component of ecology and evolution that combines both demographic and genetic processes, such as gene flow and migration, genetic drift, selection, and population extinction. Recent advances in both molecular biology and theory have revolutionized the field and have not only expanded the availability of data but also facilitated accessibility and interpretation of current data. These new techniques allow analysis of genetic similarity among populations to be coupled with phylogeography and the distribution of genotypes within and among populations relative to the history of those genotypes. The numerous case studies described herein illustrate the growing impact of geographic structure on insect science, as well as the importance of insect model systems for understanding general concepts in ecology and evolution.
Biological Control with Trichogramma: Advances, Successes, and Potential of Their Use
Authors: Smith Sandy M.
Published: July 2003

Major contributions to the release of Trichogramma for biological control of lepidopterous pests have been made in the past 20 years. Most trials have used only five species of Trichogramma against two pests; Ostrinia in corn is considered the most universally feasible. All Trichogramma programs must address the following four aspects to be successful commercially. Selection of the appropriate population is based on inter- and intraspecific variation, as well as on current definitions of parasitoid quality. Mass rearing is comprised of both host and parasitoid components, although major emphasis is now on developing artificial systems. Effective distribution of Trichogramma requires supportive extension and advanced technology. Strategies for use in the field vary according to the approach desired (inundative or inoculative), the timing, frequency and rate of release, and the multiple factors that affect release, such as the weather, crop, host, predation, pesticides, and dispersal. The past difficulty in assessing the efficacy of Trichogramma should be improved with new guidelines for standardizing terminology and measurements.
Avian Molecular Systematics, 1970s to 1990s
Authors: Sheldon Frederick H. , Bledsoe Anthony H.
Published: July 2003

We assessed the current state of avian molecular systematics by (i) considering some of the historical factors that have shaped the field in the last 20 years, (ii) reviewing the most commonly used molecular methods, and (iii) comparing higher-level phylogenies via congruence analysis. This three-pronged approach permitted us to identify strongly supported aspects of avian phylogeny and to propose technological and methodological explanations when congruence was low. We found, in general, that few areas of higher-level avian phylogeny are well supported and, hence, well understood. One main reason for this is that, despite a great deal of effort, few studies of higher-level avian phylogenetic relationships have been well planned and executed. Some investigations, for example, have gone astray because of preconceptions about rates of molecular evolution and monophyly, and others suffer from such problems as failure to find the shortest tree, lack of an outgroup, use of a nonmetric distance measure, and simple mistakes. This is not to say, however, that available techniques are incapable of reconstructing avian phylogeny. The extent of congruence that we found among branching patterns estimated by different methods, including carefully designed cladistic morphological analyses, indicates that when applied appropriately, a variety of methods provide useful insight into phylogeny.
EDWARD LAWRIE TATUM
Authors: Lederberg Joshua
Published: July 2003

Edward L. Tatum's contributions to the founding of biochemical genetics and of bacterial genetics were instrumental in the transformation of modern biology, which increasingly has focused on the flow of information through nucleic acids and the protein structure of the cell.

Tatum was most effective in collaborative investigations, in which he played the role of microbiologist and biochemist, meeting challenges of profound genetic interest. In these studies, he was instrumental in the development of microorganisms such as Neurospora and Escherichia coli as tools for fundamental genetic investigations. In 1958, he shared the Nobel Prize in Physiology and Medicine with G. W. Beadle and J. Lederberg, having been a principal partner in these separate, major lines of research.
THE GENETICS OF FLOWER DEVELOPMENT: From Floral Induction to Ovule Morphogenesis
Authors: Weigel Detlef
Published: July 2003

Flower development consists of several phases. The first step is the transition from vegetative to reproductive development, regulated by floral induction. Later steps include the initiation of individual flowers, the determination of organ identity, and organ-specific differentiation. One of the major discoveries of plant biology is that the genetic network controlling flower development is highly conserved in two distantly related dicots, Arabidopsis thaliana and Antirrhinum majus, and probably in other species as well. Classical genetics has identified a sizable number of genes regulating flower development, and many of these regulatory genes have been cloned. This review summarizes recent advances in the understanding of the genetic control of floral induction and determination of flower-meristem identity, with the focus on Arabidopsis thaliana. In addition, recent work on ovule morphogenesis, a late process in flower development, is discussed.
Superantigens: Mechanism of T-Cell Stimulation and Role in Immune Responses
Authors: Herman Andrew , Kappler John W. , Marrack Philippa , Pullen Ann M.
Published: July 2003

Superantigens combine with MHC class-II molecules to form the ligands that stimulate T cells via the Vβ element of the T-cell receptor. Two groups of superantigens have been described so far: first, endogenous murine products that include the MIs determinants, and second, bacterial products such as the Staphylococcal enterotoxins.

Here, we review studies that address the interactions between the foreign superantigens and MHC class-II molecules, the mechanism of T-cell stimulation, and the role that tolerance to self -superantigens plays in shaping the T-cell repertoire. We speculate on the possible evolutionary significance of superantigens.
Immunological Memory
Authors: Gray David
Published: July 2003

The past five or six years has seen a resurgence of interest in immunological memory. Areas in which important advances have been made of late or in which problems in understanding persist are covered here: (i) Selection of virgin B cells for entry into the peripheral pool. (ii) Expression of immunoglobulin isotypes and other markers on memory B cells. (iii) Development of memory B cells as a separate lineage from primary response B cells. (iv) Sites of production of memory B cells. (v) Signals that rescue mutating B cells in germinal centers, forming the basis of affinity selection, and programming further differentiation. (vi) The myriad markers of memory T cells, in particular CD45R isoforms. (vii) Selective migration pathways of memory T cells and its possible molecular basis. (viii) The lifespan of memory cells and factors that influence their long-term survival. The data accumulated during this period which have vastly increased our understanding of memory have at the same time highlighted unresolved problems that could block further progress in the field. The thorny question that we cannot at present answer is: How does a memory cell differ from an activated cell and, in the case of T cells, from an effector cell? The problem bears on the interpretation of any study that sets out to correlate memory phenotype with memory function. Immunologists may have donned an intellectual straitjacket in their search for the memory cell.
The Role of Autoantibodies in Autoimmune Disease
Authors: Naparstek Yaakov , Plotz Paul H.
Published: July 2003

In autoimmune diseases, autoantibodies may be the actual pathogenetic agents of the disease, the secondary consequences of tissue damage, or the harmless footprints of an etiologic agent. Establishing a pathogenetic role for autoantibodies requires that they meet stringent criteria. It appears that the location of the presumptive target antigen most critically influences the pathogenetic potential of autoantibodies. Autoantibodies directed against cell surface targets, such as hormone receptors, are clearly pathogenetic; those directed against extracellular targets, such as circulating molecules or extracellular matrix, may or may not cause any damage. Those apparently directed against intracellular targets are usually not pathogenetic unless it can be clearly demonstrated (a) that the antigen is released from within the cell so that it can bind onto a cell surface receptor or other extracellular location, such as proteinase 3; (b) that the antigen moves to an aberrant site on the cell surface, such as, perhaps, the small ribonucleoprotein antigen Ro; or (c) that a cross-reactive molecule, the actual target, such as the membrane ribosomal P-like protein, is at an accessible location.
The Wisdom of Hindsight
Authors: Cohn Melvin
Published: July 2003

This essay is a highly personalized account of some of the important conceptual contributions to immunology. I have asked myself, “What were the ideas that caught my attention and how and by whom were they presented?” I have learned that most of what immunologists have called concepts deal with too small a slice of the subject. They are essentially inductive extrapolations from one experiment to a possible next step. Historically, these extrapolations extended over too narrow a chasm to account for the information available at the time. The result was that an extrapolation from one misleading observation could dominate and distort, for a significant time, the course of the field. It is also why there has been an inverse relationship between the clarity of a theory and its ease of acceptance by immunologists. Looking to the past, I have used two areas to illustrate the role of conceptualization: the self-nonself discrimination and the origin of the humoral repertoire. To illustrate all of this I have chosen as a cast & characters the founding fathers of immunologays we know it today. I hope that by taking this look into the rear view mirror our efforts will be guided in more productive ways. The take-home lesson is that we need to widen our horizon constantly to make more general concepts that then render the manipulation of the immune system more useful.