Showing papers by "Iowa State University published in 2000"

RRT-connect: An efficient approach to single-query path planning

Abstract: A simple and efficient randomized algorithm is presented for solving single-query path planning problems in high-dimensional configuration spaces. The method works by incrementally building two rapidly-exploring random trees (RRTs) rooted at the start and the goal configurations. The trees each explore space around them and also advance towards each other through, the use of a simple greedy heuristic. Although originally designed to plan motions for a human arm (modeled as a 7-DOF kinematic chain) for the automatic graphic animation of collision-free grasping and manipulation tasks, the algorithm has been successfully applied to a variety of path planning problems. Computed examples include generating collision-free motions for rigid objects in 2D and 3D, and collision-free manipulation motions for a 6-DOF PUMA arm in a 3D workspace. Some basic theoretical analysis is also presented.

Relaxation in glassforming liquids and amorphous solids

Abstract: The field of viscous liquid and glassy solid dynamics is reviewed by a process of posing the key questions that need to be answered, and then providing the best answers available to the authors and their advisors at this time. The subject is divided into four parts, three of them dealing with behavior in different domains of temperature with respect to the glass transition temperature, Tg , and a fourth dealing with ‘‘short time processes.’’ The first part tackles the high temperature regime T.Tg ,i n which the system is ergodic and the evolution of the viscous liquid toward the condition at Tg is in focus. The second part deals with the regime T;Tg , where the system is nonergodic except for very long annealing times, hence has time-dependent properties ~aging and annealing!. The third part discusses behavior when the system is completely frozen with respect to the primary relaxation process but in which secondary processes, particularly those responsible for ‘‘superionic’’ conductivity, and dopart mobility in amorphous silicon, remain active. In the fourth part we focus on the behavior of the system at the crossover between the low frequency vibrational components of the molecular motion and its high frequency relaxational components, paying particular attention to very recent developments in the short time dielectric response and the high Q mechanical response. © 2000 American Institute of Physics.@S0021-8979~00!02213-1#

Genome evolution in polyploids

Abstract: Polyploidy is a prominent process in plants and has been significant in the evolutionary history of vertebrates and other eukaryotes. In plants, interdisciplinary approaches combining phylogenetic and molecular genetic perspectives have enhanced our awareness of the myriad genetic interactions made possible by polyploidy. Here, processes and mechanisms of gene and genome evolution in polyploids are reviewed. Genes duplicated by polyploidy may retain their original or similar function, undergo diversification in protein function or regulation, or one copy may become silenced through mutational or epigenetic means. Duplicated genes also may interact through inter-locus recombination, gene conversion, or concerted evolution. Recent experiments have illuminated important processes in polyploids that operate above the organizational level of duplicated genes. These include inter-genomic chromosomal exchanges, saltational, non-Mendelian genomic evolution in nascent polyploids, inter-genomic invasion, and cytonuclear stabilization. Notwithstanding many recent insights, much remains to be learned about many aspects of polyploid evolution, including: the role of transposable elements in structural and regulatory gene evolution; processes and significance of epigenetic silencing; underlying controls of chromosome pairing; mechanisms and functional significance of rapid genome changes; cytonuclear accommodation; and coordination of regulatory factors contributed by two, sometimes divergent progenitor genomes. Continued application of molecular genetic approaches to questions of polyploid genome evolution holds promise for producing lasting insight into processes by which novel genotypes are generated and ultimately into how polyploidy facilitates evolution and adaptation.

The Phonology of English as an International Language

Abstract: This book advocates a new approach to English pronunciation teaching, in which the goal is mutual intelligibility among non-native speakers, rather than the imitation of native speakers. English pronunciation is considered in an international context, with the emphasis on phonological intelligibility for listeners for whom English is not their first language. The author proposes a new pronunciation syllabus, the Lingua Franca Core, based on findings from empirical research where English pronunciation is examined in its sociolinguistic context.

Disciplinary Discourses: Social Interactions in Academic Writing

Abstract: Why do engineers "report" while philosophers "argue" and biologists "describe"? In the Michigan Classics Edition of "Disciplinary Discourses: Social Interactions in Academic" "Writing," Ken Hyland examines the relationships between the cultures of academic communities and their unique discourses. Drawing on discourse analysis, corpus linguistics, and the voices of professional insiders, Ken Hyland explores how academics use language to organize their professional lives, carry out intellectual tasks, and reach agreement on what will count as knowledge. In addition, "Disciplinary Discourses" presents a useful framework for understanding the interactions between writers and their readers in published academic writing. From this framework, Hyland provides practical teaching suggestions and points out opportunities for further research within the subject area. As issues of linguistic and rhetorical expression of disciplinary conventions are becoming more central to teachers, students, and researchers, the careful analysis and straightforward style of "Disciplinary Discourses" make it a remarkable asset. The Michigan Classics Edition features a new preface by the author and a new foreword by John M. Swales.

A survey and overview of habitat fragmentation experiments.

Abstract: Habitat destruction and fragmentation are the root causes of many conservation problems. We conducted a literature survey and canvassed the ecological community to identify experimental studies of terrestrial habitat fragmentation and to determine whether consistent themes were emerging from these studies. Our survey revealed 20 fragmentation experiments worldwide. Most studies focused on effects of fragmentation on species richness or on the abundance(s) ofparticular species. Other important themes were the effect offragmentation in interspecific interactions, the role of corridors and landscape connectivity in in- dividual movements and species richness, and the influences of edge effects on ecosystem services. Our com- parisons showed a remarkable lack of consistency in results across studies, especially with regard to species richness and abundance relative to fragment size. Experiments with arthropods showed the best fit with the- oretical expectations of greater species richness on larger fragments. Highly mobile taxa such as birds and mammals, early-successional plant species, long-lived species, and generalist predators did not respond in the "expected" manner. Reasons for these discrepancies included edge effects, competitive release in the habitat fragments, and the spati.al scale of the experiments. One of the more consistently supported hypotheses was that movement and species richness are positively affected by corridors and connectivity, respectively. Tran- sient effects dominated many systems;,for example, crowding of individuals on fragments commonly was ob- served afterfragmentation, followed by a relaxation toward lower abundance in subsequentyears. The three long-term studies (?14 years) revealed strong patterns that would have been missed in short-term investiga- tions. Our results emphasize the wide range of species-specific responses to fragmentation, the need for eluci- dation of behavioral mechanisms affecting these responses, and the potentialfor changing responses to frag- mentation over time.

Video games and aggressive thoughts, feelings, and behavior in the laboratory and in life.

Abstract: Two studies examined violent video game effects on aggression-related variables. Study 1 found that real-life violent video game play was positively related to aggressive behavior and delinquency. The relation was stronger for individuals who are characteristically aggressive and for men. Academic achievement was negatively related to overall amount of time spent playing video games. In Study 2, laboratory exposure to a graphically violent video game increased aggressive thoughts and behavior. In both studies, men had a more hostile view of the world than did women. The results from both studies are consistent with the General Affective Aggression Model, which predicts that exposure to violent video games will increase aggressive behavior in both the short term (e.g., laboratory aggression) and the long term (e.g., delinquency).

Vegetation and soil respiration: correlations and controls.

Abstract: Soil respiration rates vary significantly among major plant biomes, suggesting that vegetation type influences the rate of soil respiration. However, correlations among climatic factors, vegetation distributions, and soil respiration rates make cause-effect arguments difficult. Vegetation may affect soil respiration by influencing soil microclimate and structure, the quantity of detritus supplied to the soil, the quality of that detritus, and the overall rate of root respiration. At the global scale, soil respiration rates correlate positively with litterfall rates in forests, as previously reported, and with aboveground net primary productivity in grasslands, providing evidence of the importance of detritus supply. To determine the direction and magnitude of the effect of vegetation type on soil respiration, we collated data from published studies where soil respiration rates were measured simultaneously in two or more plant communities. We found no predictable differences in soil respiration between cropped and vegetation-free soils, between forested and cropped soils, or between grassland and cropped soils, possibly due to the diversity of crops and cropping systems included. Factors such as temperature, moisture availability, and substrate properties that simultaneously influence the production and consumption of organic matter are more important in controlling the overall rate of soil respiration than is vegetation type in most cases. However, coniferous forests had ∼10% lower rates of soil respiration than did adjacent broad-leaved forests growing on the same soil type, and grasslands had, on average, ∼20% higher soil respiration rates than did comparable forest stands, demonstrating that vegetation type does in some cases significantly affect rates of soil respiration.

The relational-interdependent self-construal and relationships.

Abstract: Three studies describe the development and validation of a measure of the relational-interdependent self-construal, which is defined as the tendency to think of oneself in terms of relationships with close others. Study 1 reports the development, psychometric properties, and tests of validity of this new measure. Individuals who scored high on the Relational-Interdependent Self-Construal (RISC) Scale characterized their important relationships as closer and more committed than did individuals who scored low on this measure (Study 1) and were more likely to take into account the needs and wishes of others when making decisions (Study 2). In Study 3, using a dyadic interaction paradigm with previously unacquainted participants, the partners of persons who scored high on the RISC scale viewed them as open and responsive to their needs and concerns; these perceptions were related to positive evaluations of the relationship.

Religious Involvement and Mortality: A Meta-Analytic Review

Abstract: A meta-analysis of data (mm 42 independent samples examining the association of a measure of religious involvement and all-cause mortality is reported. Religious involvement was significantly associated with lower mortality (odds ratio = 1.29; 95% confidence interval: 1.20-1.39), indicating that people high in religious involvement were more likely to be alive at follow-up than people lower in religious involvement. Although the strength of the religious involvement-mortality association varied as a function of several moderator variables, the association of religious involvement and mortality was robust and on the order of magnitude that has come to be expected for psychosocial factors. Conclusions did not appear to be due to publication bias.

The influence of cause-related marketing on consumer choice: Does one good turn deserve another?

Abstract: Are consumers more likely to select brands offered by companies that engage in cause-related marketing (CRM)? Somewhat surprisingly, little evidence exists that directly addresses this issue. Accordingly, the present examination investigates whether and when CRM efforts influence consumer choice. The results from several studies indicate that information regarding a company’s support of social causes can affect choice. However, CRM’s influence on choice is found to depend on the perceived motivation underlying the company’s CRM efforts as well as whether consumers must trade off company sponsorship of causes for lower performance or higher price. The results also indicate that CRM cues affect choice primarily through compensatory strategies involving trade-offs rather than through noncompensatory strategies. Implications of the current findings for existing theory are discussed along with directions for future research.

The effects of extrinsic product cues on consumers’ perceptions of quality, sacrifice, and value

Abstract: The authors report the results of two experiments designed to test the effects of extrinsic cues—price, brand name, store name, and country of origin—on consumers’ perceptions of quality, sacrifice, and value. The results of the experiments support hypothesized linkages between (a) each of the four experimentally manipulated extrinsic cues and perceived quality, (b) price and perceived sacrifice, (c) perceived quality and perceived value, and (d) perceived sacrifice and perceived value. The results also indicate that the linkages between the extrinsic cues and perceived value are mediated by perceived quality and sacrifice.

The Sustainability of University-Industry Research Collaboration: An Empirical Assessment

Abstract: The concept of university-industry collaboration is an important social experiment in the nation's innovation system. This study examines the sustainability of this collaborative experience by focusing on the actual “give-and-take” outcomes between university faculty members and industrial firms. Based on two separate but similar surveys conducted in 1997, one for faculty members and another for industry technology managers, the study reports that participants in research collaboration appear to realize significant benefits, some expected and others unexpected. The most significant benefit realized by firms is an increased access to new university research and discoveries, and the most significant benefits by faculty members is complementing their own academic research by securing funds for graduate students and lab equipment, and by seeking insights into their own research. Reflecting on their collaborative experience, an overwhelming majority of these participants say that in the future they would expand or at least sustain the present level of collaboration.

Measurement Issues in the Assessment of Physical Activity in Children

Abstract: This paper reviewed the nature of children's physical activity patterns and how the unique nature of children can impact the assessment of physical activity. To accurately assess children's activity patterns, an instrument must be sensitive enough to detect, code, or record sporadic and intermittent activity. Care also must be used to select criterion measures that reflect appropriate physical activity guidelines for children. A number of different measurement approaches have been described for assessing children's activity, but no specific method can be identified as the best option for all studies. Selection of an appropriate instrument depends on the specific research question being addressed as well as the relative importance of accuracy and practicality (Baranowski & Simons-Morton, 1991). For example, accurate measures of energy expenditure using doubly-labeled water, indirect calorimetry, or heart rate calibration equations may be needed for certain clinical studies, but the cost and inconvenience would make them impractical for field-based assessments on larger samples. The "accuracy-practicality" trade-off presents a more challenging predicament with children than for adults. In adults, a number of self-report instruments have been found useful for large epidemiological studies or interventions where less precision is needed. Because of developmental differences, especially in ability to think abstractly and perform detailed recall (Going et al., 1999; Sallis, 1991), children are less likely to make accurate self-report assessment than adults. Though self-report methods are still likely to be a principal source of information for many studies, other approaches (or the use of combined measures) may be needed to better characterize children's activity levels. While objective instruments (e.g., direct observation or activity monitoring) require more time and resources than self-report, there are options available to simplify data collection. One approach may be to focus assessments on key times or places that allow children to be active. The time after school, for example, appears to be a critical period that defines their propensity for physical activity (Hager, 1999). Monitoring of entire groups for discrete periods of time (e.g., recess or physical education) may also be useful to understand variability in activity patterns since children would all be exposed to the same stimulus or opportunity to be active. Proxy measures may also be useful in studying activity in children. For example, several studies (Baranowski, Thompson, DuRant, Baranowski, & Puhl, 1993; Sallis et al., 1993) have demonstrated that time spent outside is strongly predictive of activity in children. Involvement in community sports programs may also be a useful proxy measure as sports programs have been found to account for approximately 55-65% of children's moderate to vigorous activity (Katzmarzyk & Malina, 1999). Another option for improving assessments in children is to employ multiple measures of physical activity. A number of studies (Coleman, Saelens, Wiedrich-Smith, Finn, & Epstein, 1997; McMurray et al., 1998; Sallis et al., 1998; Simons-Morton et al., 1994) have reported differences in levels of activity when activity monitors were compared with self-report data. The method of measurement has also been shown to influence the results of studies on the determinants of physical activity in children (Epstein, Paluch, Coleman, Vito, & Anderson, 1996). While we do not currently know which measure is most accurate, reporting the results with different instruments provides a more complete description of children's activity and permit a triangulation of outcomes. In summary, there remains no single way of obtaining a highly accurate account of physical activity or energy expenditure in children. The nature of children's movement patterns, the various types of activities engaged in, and the inherent limitations of each assessment tool limit the ultima

Learning to Lead in Higher Education

Abstract: Learning to Lead in Higher Education, by Paul Ramsden. New York: Routledge, 1998. 288 pp. $75.00 (24.99) Is academic leadership an oxymoron or a serious field of study? Until 20 years ago the major works on academic leadership focused on the roles of presidents and chief academic officers. The literature on academic department chairs was silent, with most of the information and attention coming from anecdotal speeches, professional papers, popular journal articles, a couple of text-type books, and a few data-based studies. Two decades ago the main reference for department chairs was Allen Tucker's Chairing the Academic Department (1981). Through the 1980s the academic department chair remained the least studied and most misunderstood position in the academy. Although many education scholars wrote about the organization and governance of higher education, relatively little was known about those who led and supported academic units. In addition, the management role of the department chair has no parallel in business and industry, or education for that matter. Typical faculty manuals at most colleges and universiti es provide a list of chairs' duties and responsibilities but do not provide insight into department leadership. The 1990s brought an onslaught of new publications shedding light on the overshadowed role of department chair. In 1990 John Creswell and his colleagues introduced The Academic Chairperson's Handbook, followed by Gmelch and Miskin's Leadership Skills for Department Chairs (1993), Ann Lucas's Strengthening Leadership: A Team-Building Guide for Chairs in Colleges and Universities (1994), Mary Lou Higgerson's Communication Skills for Department Chairs (1996), and Irene Hecht and her colleagues' recently released The Department Chair as Academic Leader (1999). Australian scholars extrapolated the role of the department head from English and American writings and studies until the release of Moses and Roe's (1990) ground-breaking work on Australian department heads and Sarros and Gmelch's replication of American department chair research in Australia (1996). Within this context Paul Ramsden's book Learning to Lead in Higher Education represents the second major work written for academic department leaders based on the Australian experience. Whereas Moses and Roe illuminated the world of the chair/head within the department, Ramsden looks at the role as part of a larger institutional nexus. In the introductory chapter Ramsden posits a simple three-stage systems model of presage-process-product to understand the challenges faced by academic leaders. Chapter 2 empirically addresses the presage or environmental factors of changing external forces on higher education (knowledge differentiation, mass higher education, and reduced public funding) and internal characteristics of universities (academic values and culture). Chapter 3 explores aspects of the academic outcomes or products constituting the third part of the model, underscoring the leader's job to increase productivity. He follows up in Chapters 4 and 5 with evidence suggesting that departmental leadership and intellectual climate can influence the output of research productivity and effective teaching. Chapter 6 concludes Part I with an inconclusive exploration of whether there are any useful leadership principles common to both university and other organizations. Ramsden postulates a series of principles characterizing competent academic leadership: a dynamic process, an outcomes-focused agenda, a phenomenon of both personal and organizational development, a relationship between leaders and followers, and a personal transformation process through reflection and learning. The second and third parts of the book attempt to demonstrate ways to manage in order to improve the context of academic work. Ramsden argues (unconvincingly in the opinion of this reviewer) that the framework for improving university teaching is similar to the practice of academic leadership. …

Sample size requirements for estimating pearson, kendall and spearman correlations

Abstract: Interval estimates of the Pearson, Kendall tau-a and Spearman correlations are reviewed and an improved standard error for the Spearman correlation is proposed. The sample size required to yield a confidence interval having the desired width is examined. A two-stage approximation to the sample size requirement is shown to give accurate results.

YidC mediates membrane protein insertion in bacteria.

Abstract: The basic machinery for the translocation of proteins into or across membranes is remarkably conserved from Escherichia coli to humans. In eukaryotes, proteins are inserted into the endoplasmic reticulum using the signal recognition particle (SRP) and the SRP receptor, as well as the integral membrane Sec61 trimeric complex (composed of alpha, beta and gamma subunits). In bacteria, most proteins are inserted by a related pathway that includes the SRP homologue Ffh, the SRP receptor FtsY, and the SecYEG trimeric complex, where Y and E are related to the Sec61 alpha and gamma subunits, respectively. Proteins in bacteria that exhibit no dependence on the Sec translocase were previously thought to insert into the membrane directly without the aid of a protein machinery. Here we show that membrane insertion of two Sec-independent proteins requires YidC. YidC is essential for E. coli viability and homologues are present in mitochondria and chloroplasts. Depletion of YidC also interferes with insertion of Sec-dependent membrane proteins, but it has only a minor effect on the export of secretory proteins. These results provide evidence for an additional component of the translocation machinery that is specialized for the integration of membrane proteins.

Integration of soil, crop and weed management in low-external-input farming systems

Abstract: Greater adoption and refinement of low-external-input (LEI) farming systems have been proposed as ways to ameliorate economic, environmental and health problems associated with conventional farming systems. Organic soil amendments and crop diversification are basic components of LEI systems. Weed scientists can improve the use of these practices for weed management by improving knowledge of four relevant ecological mechanisms. First, multispecies crop rotations, intercrops and cover crops may reduce opportunities for weed growth and regeneration through resource competition and niche disruption. Secondly, weed species appear to be more susceptible to phytotoxic effects of crop residues and other organic soil amendments than crop species, possibly because of differences in seed mass. Thirdly, delayed patterns of N availability in LEI systems may favour large-seeded crops over small-seeded weeds. Finally, additions of organic materials can change the incidence and severity of soil-borne diseases affecting weeds and crops. Our research on LEI sweetcorn and potato production systems in central and northern Maine (USA) suggests that these mechanisms can reduce weed density and growth while maintaining crop yields. Low-external-input farming systems will advance most quickly through the application of interdisciplinary research focused on these and other ecological mechanisms.

Self-Esteem, Narcissism, and Aggression Does Violence Result From Low Self-Esteem or From Threatened Egotism?

Abstract: A traditional view holds that low self-esteem causes ag- gression, but recent work has not confirmed this. Although aggressive people typically have high self-esteem, there are also many nonaggressive people with high self-esteem, and so newer constructs such as narcissism and unstable self- esteem are most effective at predicting aggression. The link between self-regard and ag- gression is best captured by the theory of threatened egotism, which depicts aggression as a means of defending a highly favorable view of self against someone who seeks to under- mine or discredit that view. vided strong empirical evidence that low self-esteem causes aggres- sion. Ironically, the theory seemed to enter into conventional wisdom without ever being empirically es- tablished. The view of low self-esteem that has emerged from many research studies does not, however, seem easily reconciled with the theory that low self-esteem causes aggres- sion. A composite of research find- ings depicts people with low self- esteem as uncertain and confused about themselves, oriented toward avoiding risk and potential loss, shy, modest, emotionally labile (and having tendencies toward de- pression and anxiety), submitting readily to other people's influence, and lacking confidence in them- selves (see compilation by Bau- meister, 1993). None of these patterns seems likely to increase aggression, and some of them seem likely to dis- courage it. People with low self- esteem are oriented toward avoid- ing risk and loss, whereas attacking someone is eminently risky. People with low self-esteem lack confi- dence of success, whereas aggres- sion is usually undertaken in the expectation of defeating the other person. Low self-esteem involves submitting to influence, whereas aggression is often engaged in to resist and reject external influence. Perhaps most relevant, people with low self-esteem are confused and uncertain about who they are,

Physiological astrocytic calcium levels stimulate glutamate release to modulate adjacent neurons

Abstract: Astrocytes can release glutamate in a calcium-dependent manner and consequently signal to adjacent neurons. Whether this glutamate release pathway is used during physiological signaling or is recruited only under pathophysiological conditions is not well defined. One reason for this lack of understanding is the limited knowledge about the levels of calcium necessary to stimulate glutamate release from astrocytes and about how they compare with the range of physiological calcium levels in these cells. We used flash photolysis to raise internal calcium in astrocytes, while monitoring astrocytic calcium levels and glutamate, which evoked slow inward currents that were recorded electrophysiologically from single neurons grown on microislands of astrocytes. With this approach, we demonstrate that modest changes of astrocytic calcium, from 84 to 140 nM, evoke substantial glutamatergic currents in neighboring neurons (−391 pA), with a Hill coefficient of 2.1 to 2.7. Because the agonists glutamate, norepinephrine, and dopamine all raise calcium in astrocytes to levels exceeding 1.8 μM, these quantitative studies demonstrate that the astrocytic glutamate release pathway is engaged at physiological levels of internal calcium. Consequently, the calcium-dependent release of glutamate from astrocytes functions within an appropriate range of astrocytic calcium levels to be used as a signaling pathway within the functional nervous system.

Recent progress toward understanding biosynthesis of the amylopectin crystal.

Abstract: Plant starch granules provide the largest percentage of calories in the human diet. Starch consists almost entirely of the Glc homopolymers amylopectin and amylose. Amylopectin is the major contributor to both mass and granule structure. Because of the very basic role that starch plays in our

Open reading frame 2 of porcine circovirus type 2 encodes a major capsid protein.

Abstract: Porcine circovirus 2 (PCV2), a single-stranded DNA virus associated with post-weaning multisystemic wasting syndrome of swine, has two potential open reading frames, ORF1 and ORF2, greater than 600 nucleotides in length. ORF1 is predicted to encode a replication-associated protein (Rep) essential for replication of viral DNA, while ORF2 contains a conserved basic amino acid sequence at the N terminus resembling that of the major structural protein of chicken anaemia virus. Thus far, the structural protein(s) of PCV2 have not been identified. In this study, a viral structural protein of 30 kDa was identified in purified PCV2 particles. ORF2 of PCV2 was cloned into a baculovirus expression vector and the gene product was expressed in insect cells. The expressed ORF2 gene product had a molecular mass of 30 kDa, similar to that detected in purified virus particles. The recombinant ORF2 protein self-assembled to form capsid-like particles when viewed by electron microscopy. Antibodies against the ORF2 protein were detected in samples of sera obtained from pigs as early as 3 weeks after experimental infection with PCV2. These results show that the major structural protein of PCV2 is encoded by ORF2 and has a molecular mass of 30 kDa.

A consensus linkage map of the chicken genome

Abstract: A consensus linkage map has been developed in the chicken that combines all of the genotyping data from the three available chicken mapping populations. Genotyping data were contributed by the laboratories that have been using the East Lansing and Compton reference populations and from the Animal Breeding and Genetics Group of the Wageningen University using the Wageningen/Euribrid population. The resulting linkage map of the chicken genome contains 1889 loci. A framework map is presented that contains 480 loci ordered on 50 linkage groups. Framework loci are defined as loci whose order relative to one another is supported by odds greater then 3. The possible positions of the remaining 1409 loci are indicated relative to these framework loci. The total map spans 3800 cM, which is considerably larger than previous estimates for the chicken genome. Furthermore, although the physical size of the chicken genome is threefold smaller then that of mammals, its genetic map is comparable in size to that of most mammals. The map contains 350 markers within expressed sequences, 235 of which represent identified genes or sequences that have significant sequence identity to known genes. This improves the contribution of the chicken linkage map to comparative gene mapping considerably and clearly shows the conservation of large syntenic regions between the human and chicken genomes. The compact physical size of the chicken genome, combined with the large size of its genetic map and the observed degree of conserved synteny, makes the chicken a valuable model organism in the genomics as well as the postgenomics era. The linkage maps, the two-point lod scores, and additional information about the loci are available at web sites in Wageningen (http://www.zod.wau.nl/vf/research/chicken/frame_chicken.html) and East Lansing (http://poultry.mph.msu.edu/).

SNARE Protein-Dependent Glutamate Release from Astrocytes

Abstract: We investigated the cellular mechanisms underlying the Ca(2+)-dependent release of glutamate from cultured astrocytes isolated from rat hippocampus. Using Ca(2+) imaging and electrophysiological techniques, we analyzed the effects of disrupting astrocytic vesicle proteins on the ability of astrocytes to release glutamate and to cause neuronal electrophysiological responses, i.e., a slow inward current (SIC) and/or an increase in the frequency of miniature synaptic currents. We found that the Ca(2+)-dependent glutamate release from astrocytes is not caused by the reverse operation of glutamate transporters, because the astrocyte-induced glutamate-mediated responses in neurons were affected neither by inhibitors of glutamate transporters (beta-threo-hydroxyaspartate, dihydrokainate, and L-trans-pyrrolidine-2,4-dicarboxylate) nor by replacement of extracellular sodium with lithium. We show that Ca(2+)-dependent glutamate release from astrocytes requires an electrochemical gradient necessary for glutamate uptake in vesicles, because bafilomycin A(1), a vacuolar-type H(+)-ATPase inhibitor, reduced glutamate release from astrocytes. Injection of astrocytes with the light chain of the neurotoxin Botulinum B that selectively cleaves the vesicle-associated SNARE protein synaptobrevin inhibited the astrocyte-induced glutamate response in neurons. Therefore, the Ca(2+)-dependent glutamate release from astrocytes is a SNARE protein-dependent process that requires the presence of functional vesicle-associated proteins, suggesting that astrocytes store glutamate in vesicles and that it is released through an exocytotic pathway.

Divergent Evolution of Plant NBS-LRR Resistance Gene Homologues in Dicot and Cereal Genomes

Abstract: The majority of plant disease resistance genes are members of very large multigene families. They encode structurally related proteins containing nucleotide binding site domains (NBS) and C-terminal leucine rich repeats (LRR). The N-terminal region of some resistance genes contain a short sequence called TIR with homology to the animal innate immunity factors, Toll and interleukin receptor-like genes. Only a few plant resistance genes have been functionally analyzed and the origin and evolution of plant resistance genes remain obscure. We have reconstructed gene phylogeny by exhaustive analysis of available genome and amplified NBS domain sequences. Our study shows that NBS domains faithfully predict whole gene structure and can be divided into two major groups. Group I NBS domains contain group-specific motifs that are always linked with the TIR sequence in the N terminus. Significantly, Group I NBS domains and their associated TIR domains are widely distributed in dicot species but were not detected in cereal databases. Furthermore, Group I specific NBS sequences were readily amplified from dicot genomic DNA but could not be amplified from cereal genomic DNA. In contrast, Group II NBS domains are always associated with putative coiled-coil domains in their N terminus and appear to be present throughout the angiosperms. These results suggest that the two main groups of resistance genes underwent divergent evolution in cereal and dicot genomes and imply that their cognate signaling pathways have diverged as well.