Showing papers by "Washington State University published in 2001"

Sequence complexity of disordered protein.

Abstract: Intrinsic disorder refers to segments or to whole proteins that fail to self-fold into fixed 3D structure, with such disorder sometimes existing in the native state. Here we report data on the relationships among intrinsic disorder, sequence complexity as measured by Shannon's entropy, and amino acid composition. Intrinsic disorder identified in protein crystal structures, and by nuclear magnetic resonance, circular dichroism, and prediction from amino acid sequence, all exhibit similar complexity distributions that are shifted to lower values compared to, but significantly overlapping with, the distribution for ordered proteins. Compared to sequences from ordered proteins, these variously characterized intrinsically disordered segments and proteins, and also a collection of low-complexity sequences, typically have obviously higher levels of protein-specific subsets of the following amino acids: R, K, E, P, and S, and lower levels of subsets of the following: C, W, Y, I, and V. The Swiss Protein database of sequences exhibits significantly higher amounts of both low-complexity and predicted-to-be-disordered segments as compared to a non-redundant set of sequences from the Protein Data Bank, providing additional data that nature is richer in disordered and low-complexity segments compared to the commonness of these features in the set of structurally characterized proteins.

Teamwork Quality and the Success of Innovative Projects: A Theoretical Concept and Empirical Evidence

Abstract: An extensive body of literature indicates the importance of teamwork to the success of innovative projects. This growing awareness, that "good teamwork" increases the success of innovative projects, raises new questions: What is teamwork, and how can it be measured? Why and how is teamwork related to the success of innovative projects? How strong is the relationship between teamwork and various measures of project success such as performance or team member satisfaction? This article develops a comprehensive concept of the collaboration in teams, called Teamwork Quality (TWQ). The six facets of the TWQ construct, i.e., communication, coordination, balance of member contributions, mutual support, effort, and cohesion, are specified. Hypotheses regarding the relationship between TWQ and project success are tested using data from 575 team members, team leaders, and managers of 145 German software teams. The results of the structural equation models estimated show that TWQ (as rated by team members) is significantly associated with team performance as rated by team members, team leaders, and team-external managers. However, the magnitude of the relationship between TWQ and team performance varies by the perspective of the performance rater, i.e., manager vs. team leader vs. team members. Furthermore, TWQ shows a strong association with team members' personal success (i.e., work satisfaction and learning).

Timing of Millennial-Scale Climate Change in Antarctica and Greenland During the Last Glacial Period

Abstract: A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a “bipolar see-saw” in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales.

The composite genome of the legume symbiont Sinorhizobium meliloti.

Abstract: The scarcity of usable nitrogen frequently limits plant growth. A tight metabolic association with rhizobial bacteria allows legumes to obtain nitrogen compounds by bacterial reduction of dinitrogen (N2) to ammonium (NH4+). We present here the annotated DNA sequence of the alpha-proteobacterium Sinorhizobium meliloti, the symbiont of alfalfa. The tripartite 6.7-megabase (Mb) genome comprises a 3.65-Mb chromosome, and 1.35-Mb pSymA and 1.68-Mb pSymB megaplasmids. Genome sequence analysis indicates that all three elements contribute, in varying degrees, to symbiosis and reveals how this genome may have emerged during evolution. The genome sequence will be useful in understanding the dynamics of interkingdom associations and of life in soil environments.

Cheating in Academic Institutions: A Decade of Research

Abstract: This article reviews 1 decade of research on cheating in academic institutions. This research demonstrates that cheating is prevalent and that some forms of cheating have increased dramatically in the last 30 years. This research also suggests that although both individual and contextual factors influence cheating, contextual factors, such as students' perceptions of peers' behavior, are the most powerful influence. In addition, an institution's academic integrity programs and policies, such as honor codes, can have a significant influence on students' behavior. Finally, we offer suggestions for managing cheating from students' and faculty members' perspectives.

Building Organizational Capabilities for Managing Economic Crisis: The Role of Market Orientation and Strategic Flexibility:

Abstract: Firms around the world often must manage and survive economic crises. Recent cases in Asia, Eastern Europe, and South America bear testimony to this point. As economic weak spots are integrated into the global economy, it is timely to develop an understanding of organizational capabilities that can help firms manage their way through such crises. The authors investigate the role of market orientation and strategic flexibility in helping Thai firms manage the recent Asian crisis. The results demonstrate the contingent nature of the influence of market orientation and strategic flexibility on firm performance after a crisis has occurred. As hypothesized, market orientation has an adverse effect on firm performance after a crisis. This effect is moderated by demand and technological uncertainty and is enhanced by competitive intensity. In contrast, strategic flexibility has a positive influence on firm performance after a crisis, which is enhanced by competitive intensity and moderated by demand and...

A Survey of Energy Efficient Network Protocols for Wireless Networks

Abstract: Wireless networking has witnessed an explosion of interest from consumers in recent years for its applications in mobile and personal communications. As wireless networks become an integral component of the modern communication infrastructure, energy efficiency will be an important design consideration due to the limited battery life of mobile terminals. Power conservation techniques are commonly used in the hardware design of such systems. Since the network interface is a significant consumer of power, considerable research has been devoted to low-power design of the entire network protocol stack of wireless networks in an effort to enhance energy efficiency. This paper presents a comprehensive summary of recent work addressing energy efficient and low-power design within all layers of the wireless network protocol stack.

Hydrogen Peroxide Acts as a Second Messenger for the Induction of Defense Genes in Tomato Plants in Response to Wounding, Systemin, and Methyl Jasmonate

Abstract: The systemic accumulation of both hydrogen peroxide (H2O2) and proteinase inhibitor proteins in tomato leaves in response to wounding was inhibited by the NADPH oxidase inhibitors diphenylene iodonium (DPI), imidazole, and pyridine. The expression of several defense genes in response to wounding, systemin, oligosaccharides, and methyl jasmonate also was inhibited by DPI. These genes, including those of four proteinase inhibitors and polyphenol oxidase, are expressed within 4 to 12 hr after wounding. However, DPI did not inhibit the wound-inducible expression of genes encoding prosystemin, lipoxygenase, and allene oxide synthase, which are associated with the octadecanoid signaling pathway and are expressed 0.5 to 2 hr after wounding. Accordingly, treatment of plants with the H2O2-generating enzyme glucose oxidase plus glucose resulted in the induction of only the later-expressed defensive genes and not the early-expressed signaling-related genes. H2O2 was cytochemically detected in the cell walls of vascular parenchyma cells and spongy mesophyll cells within 4 hr after wounding of wild-type tomato leaves, but not earlier. The cumulative results suggest that active oxygen species are generated near cell walls of vascular bundle cells by oligogalacturonide fragments produced by wound-inducible polygalacturonase and that the resulting H2O2 acts as a second messenger for the activation of defense genes in mesophyll cells. These data provide a rationale for the sequential, coordinated, and functional roles of systemin, jasmonic acid, oligogalacturonides, and H2O2 signals for systemic signaling in tomato plants in response to wounding.

Functional analysis of genes for biosynthesis of pyocyanin and phenazine-1-carboxamide from Pseudomonas aeruginosa PAO1.

Abstract: Phenazine compounds produced by fluorescent Pseudomonas species are biologically active metabolites that function in microbial competitiveness (37), the suppression of soilborne plant pathogens (1, 11, 55, 56), and virulence in human and animal hosts (35). The most widely studied phenazine-producing fluorescent pseudomonad is P. aeruginosa, a gram-negative opportunistic pathogen of animals, insects, nematodes, and plants (30, 33, 35, 46). In humans, P. aeruginosa infects immunocompromised, burned, or injured patients and can cause both acute and chronic lung disease. Strains of P. aeruginosa produce a variety of redox-active phenazine compounds, including pyocyanin, phenazine-1-carboxylic acid (PCA), 1-hydroxyphenazine (1-OH-PHZ), and phenazine-1-carboxamide (PCN) (7, 52, 57). From 90 to 95% of P. aeruginosa isolates produce pyocyanin (52), and the presence of high concentrations of pyocyanin in the sputum of cystic fibrosis patients has suggested that this compound plays a role in pulmonary tissue damage observed with chronic lung infections (64). This idea is supported by several recent studies which demonstrated that pyocyanin contributes in a variety of ways to the pathophysiological effects observed in airways infected by P. aeruginosa. Pyocyanin interferes with the regulation of ion transport, ciliary beat frequency, and mucus secretion in airway epithelial cells by altering the cytosolic concentration of calcium (15). It may interact with endothelium-derived relaxing factor or with nitric oxide (which plays a central role in the control of blood pressure, blood flow, and immune function) through the formation of a complex, or it may act by inhibition of nitric oxide synthase (29, 58, 59). Phenazines that are produced by P. aeruginosa also can stimulate alveolar macrophages to produce two neutrophil chemotaxins, IL-8 and leukotriene B4, that attract neutrophils into airways, causing an inflammatory response and neutrophil-mediated tissue damage (14, 33). The unusually broad range of biological activity associated with phenazines is thought to be due to their ability to undergo redox cycling in the presence of various reducing agents and molecular oxygen, which leads to the accumulation of toxic superoxide (O2−) and hydrogen peroxide (H2O2) and eventually to oxidative cell injury or death (6, 25). It also has been shown that pyocyanin can interact synergistically with the siderophore pyochelin and with transferrin cleaved by proteases secreted by both P. aeruginosa and neutrophils in infected lungs to catalyze the formation of the highly cytotoxic hydroxyl radical (·OH), which damages pulmonary endothelial cells (6, 38). In model pathogenesis systems, phenazine synthesis by P. aeruginosa is required for the generation of disease symptoms in plants and for effective killing of the nematode Caenorhabditis elegans and the greater wax moth, Galleria mellonella (30, 35, 46). Phenazine compounds produced in the rhizosphere of plants contribute to the biological control activity of P. aeruginosa against Fusarium wilt of chickpea and Pythium damping-off of bean (1). Although the pathophysiological effects of phenazines produced by P. aeruginosa in host organisms are well studied (6, 14, 15, 33, 34, 38, 64) and pyocyanin-deficient phenotypes frequently have been described (18, 19, 26, 32, 35, 46, 54), the biochemistry and genetics of phenazine synthesis in P. aeruginosa have remained unclear. We describe here cloning and functional analysis of two seven-gene phenazine operons and three phenazine-modifying genes from P. aeruginosa PAO1. Our results show that P. aeruginosa contains a complex phenazine biosynthetic pathway consisting of two homologous core loci (phzA1B1C1D1E1F1G1 and phzA2B2C2D2E2F2G2) responsible for synthesis of PCA and three additional genes (phzM, phzS, and phzH) encoding unique enzymes involved in the conversion of PCA to pyocyanin and PCN. We detected the core biosynthetic operon by Southern hybridization in 21 phenazine-producing pseudomonads, including strains of P. aeruginosa, Pseudomonas fluorescens, Pseudomonas chlororaphis, and Pseudomonas aureofaciens, but not in seven phenazine-producing isolates of Burkholderia cepacia, Burkholderia phenazinium, and Brevibacterium iodinum. Thus, the core biosynthetic pathway is highly conserved in fluorescent Pseudomonas spp. but differs significantly from that in other phenazine-producing bacterial genera.

Gender and the Internet: Women Communicating and Men Searching

Abstract: This research examined gender differences in Internet use and factors responsible for these differences. A sample of 630 Anglo American undergraduates completed the Student Computer and Internet Survey that contained questions about e-mail and Web use, and about potential affective and cognitive mediators of use. Based on a general model of Internet use, we predicted and found that females used e-mail more than did males, males used the Web more than did females, and females reported more computer anxiety, less computer self-efficacy, and less favorable and less stereotypic computer attitudes. Path analysis to identify mediators of gender differences in Internet use revealed that computer self-efficacy, loneliness, and depression accounted in part for gender differences, but that gender continued to have a direct effect on use after these factors were considered. Implications for realizing the democratizing potential and benefits of Internet use are discussed.

Production of Polyunsaturated Fatty Acids by Polyketide Synthases in Both Prokaryotes and Eukaryotes

Abstract: Polyunsaturated fatty acids (PUFAs) are essential membrane components in higher eukaryotes and are the precursors of many lipid-derived signaling molecules. Here, pathways for PUFA synthesis are described that do not require desaturation and elongation of saturated fatty acids. These pathways are catalyzed by polyketide synthases (PKSs) that are distinct from previously recognized PKSs in both structure and mechanism. Generation of cis double bonds probably involves position-specific isomerases; such enzymes might be useful in the production of new families of antibiotics. It is likely that PUFA synthesis in cold marine ecosystems is accomplished in part by these PKS enzymes.

Plant defense in the absence of jasmonic acid: the role of cyclopentenones.

Abstract: The Arabidopsis opr3 mutant is defective in the isoform of 12-oxo-phytodienoate (OPDA) reductase required for jasmonic acid (JA) biosynthesis. Oxylipin signatures of wounded opr3 leaves revealed the absence of detectable 3R,7S-JA as well as altered levels of its cyclopentenone precursors OPDA and dinor OPDA. In contrast to JA-insensitive coi1 plants and to the fad3 fad7 fad8 mutant lacking the fatty acid precursors of JA synthesis, opr3 plants exhibited strong resistance to the dipteran Bradysia impatiens and the fungus Alternaria brassicicola. Analysis of transcript profiles in opr3 showed the wound induction of genes previously known to be JA-dependent, suggesting that cyclopentenones could fulfill some JA roles in vivo. Treating opr3 plants with exogenous OPDA powerfully up-regulated several genes and disclosed two distinct downstream signal pathways, one through COI1, the other via an electrophile effect of the cyclopentenones. We conclude that the jasmonate family cyclopentenone OPDA (most likely together with dinor OPDA) regulates gene expression in concert with JA to fine-tune the expression of defense genes. More generally, resistance to insect and fungal attack can be observed in the absence of JA.

Sustainability of three apple production systems

Abstract: Escalating production costs, heavy reliance on non-renewable resources, reduced biodiversity, water contamination, chemical residues in food, soil degradation and health risks to farm workers handling pesticides all bring into question the sustainability of conventional farming systems. It has been claimed, however, that organic farming systems are less efficient, pose greater health risks and produce half the yields of conventional farming systems. Nevertheless, organic farming became one of the fastest growing segments of US and European agriculture during the 1990s. Integrated farming, using a combination of organic and conventional techniques, has been successfully adopted on a wide scale in Europe. Here we report the sustainability of organic, conventional and integrated apple production systems in Washington State from 1994 to 1999. All three systems gave similar apple yields. The organic and integrated systems had higher soil quality and potentially lower negative environmental impact than the conventional system. When compared with the conventional and integrated systems, the organic system produced sweeter and less tart apples, higher profitability and greater energy efficiency. Our data indicate that the organic system ranked first in environmental and economic sustainability, the integrated system second and the conventional system last.

The protein trinity--linking function and disorder.

Abstract: http://biotech.nature.com • SEPTEMBER 2001 • VOLUME 19 • nature biotechnology Interpreting function in terms of specific three-dimensional structure has dominated thinking about proteins for more than 100 years, starting with the lock-and-key proposal of Fischer1 and continuing with the equating of denaturation with loss of specific structure by Wu2 and independently at a slightly later date by Mirsky and Pauling3. This dependence of function on structure is even embedded in our language: unfolded protein and denatured protein are used interchangeably. Furthermore, the avalanche of protein three-dimensional structures determined by X-ray diffraction and by nuclear magnetic resonance (NMR)4 has diverted attention away from alternative views. Numerous counterexample proteins have surfaced over the years—proteins for which lack of three-dimensional structure is required for function. One clear example is calcineurin, a serine/threonine phosphatase that becomes activated by the binding of the Ca2+–calmodulin complex to a region that exists as a disordered ensemble5,6. The disorder spans the calmodulin binding site and is essential for calcineurin function. That is, when calmodulin binds to its target helix, the helix becomes completely surrounded7. Thus, the open, flexible disordered region of calcineurin provides the space needed by calmodulin so it can completely surround its target helix. Even though hundreds of other examples of proteins with intrinsic disorder have surfaced over the past 50 years, review articles on this topic are only just now beginning to appear8–10. Wright and Dyson8 suggested that the existence of proteins with intrinsic protein disorder calls for a reassessment of the protein–structure– function paradigm. Since amino acid sequence determines three-dimensional structure, amino acid sequence should also determine lack of three-dimensional structure. Furthermore, if intrinsic disorder provides the basis for some biological functions, then the operation of natural selection should conserve the lack of folding and thereby preserve those functions that depend on this property. If disorder is indeed encoded by the amino acid sequence, then predictors of disorder should exceed the accuracies expected by chance. Work in our group has used literature and database searches to collect a set of proteins structurally characterized to have regions of disorder, some of which were indicated by NMR to be wholly disordered under physiological conditions. Using this set of proteins with intrinsic disorder, we have set out to construct the predictors needed to test the hypothesis.

Observation of all-metal aromatic molecules.

Abstract: Aromaticity is a concept invented to account for the unusual stability of an important class of organic molecules: the aromatic compounds. Here we report experimental and theoretical evidence of aromaticity in all-metal systems. A series of bimetallic clusters with chemical composition MAl4– (M = Li, Na, or Cu), was created and studied with photoelectron spectroscopy and ab initio calculations. All the MAl4– species possess a pyramidal structure containing an M+ cation interacting with a square Al42– unit. Ab initio studies indicate that Al42– exhibits characteristics of aromaticity with two delocalized π electrons (thus following the 4n + 2 electron counting rule) and a square planar structure and maintains its structural and electronic features in all the MAl4– complexes. These findings expand the aromaticity concept into the arena of all-metal species.

Silencing on the Spot. Induction and Suppression of RNA Silencing in the Agrobacterium-Mediated Transient Expression System

Abstract: The Agrobacterium-mediated transient expression assay in intact tissues has emerged as a rapid and useful method to analyze genes and gene products in plants. In many cases, high levels of active protein can be produced without the need to produce transgenic plants. In this study, a series of tools were developed to enable strong or weak induction of RNA silencing and to suppress RNA silencing in the absence of stable transgenes. Transient delivery of a gene directing production of a double-stranded green fluorescent protein (GFP) transcript rapidly induced RNA silencing of a codelivered GFP reporter gene, effectively preventing accumulation of GFP protein and mRNA. RNA silencing triggered by the strong dsGFP inducer was partially inhibited by the tobacco etch virus silencing suppressor, P1/HC-Pro. In the absence of the strong double-stranded GFP inducer, the functional GFP gene served as a weak RNA silencing inducer in the transient assay, severely limiting accumulation of the GFP mRNA over time. The weak silencing induced by the GFP gene was suppressed by P1/HC-Pro. These results indicate RNA silencing can be triggered by a variety of inducers and analyzed entirely using transient gene delivery systems. They also indicate that RNA silencing may be a significant limitation to expression of genes in the Agrobacterium-mediated transient assay but that this limitation can be overcome by using RNA silencing suppressors.

Genomic Organization of Plant Terpene Synthases and Molecular Evolutionary Implications

Abstract: Terpenoids are the largest, most diverse class of plant natural products and they play numerous functional roles in primary metabolism and in ecological interactions. The first committed step in the formation of the various terpenoid classes is the transformation of the prenyl diphosphate precursors, geranyl diphosphate, farnesyl diphosphate, and geranylgeranyl diphosphate, to the parent structures of each type catalyzed by the respective monoterpene (C(10)), sesquiterpene (C(15)), and diterpene synthases (C(20)). Over 30 cDNAs encoding plant terpenoid synthases involved in primary and secondary metabolism have been cloned and characterized. Here we describe the isolation and analysis of six genomic clones encoding terpene synthases of conifers, [(-)-pinene (C(10)), (-)-limonene (C(10)), (E)-alpha-bisabolene (C(15)), delta-selinene (C(15)), and abietadiene synthase (C(20)) from Abies grandis and taxadiene synthase (C(20)) from Taxus brevifolia], all of which are involved in natural products biosynthesis. Genome organization (intron number, size, placement and phase, and exon size) of these gymnosperm terpene synthases was compared to eight previously characterized angiosperm terpene synthase genes and to six putative terpene synthase genomic sequences from Arabidopsis thaliana. Three distinct classes of terpene synthase genes were discerned, from which assumed patterns of sequential intron loss and the loss of an unusual internal sequence element suggest that the ancestral terpenoid synthase gene resembled a contemporary conifer diterpene synthase gene in containing at least 12 introns and 13 exons of conserved size. A model presented for the evolutionary history of plant terpene synthases suggests that this superfamily of genes responsible for natural products biosynthesis derived from terpene synthase genes involved in primary metabolism by duplication and divergence in structural and functional specialization. This novel molecular evolutionary approach focused on genes of secondary metabolism may have broad implications for the origins of natural products and for plant phylogenetics in general.

Metabolic engineering of essential oil yield and composition in mint by altering expression of deoxyxylulose phosphate reductoisomerase and menthofuran synthase.

Abstract: Peppermint (Mentha × piperita L.) was independently transformed with a homologous sense version of the 1-deoxy-d-xylulose-5-phosphate reductoisomerase cDNA and with a homologous antisense version of the menthofuran synthase cDNA, both driven by the CaMV 35S promoter. Two groups of transgenic plants were regenerated in the reductoisomerase experiments, one of which remained normal in appearance and development; another was deficient in chlorophyll production and grew slowly. Transgenic plants of normal appearance and growth habit expressed the reductoisomerase transgene strongly and constitutively, as determined by RNA blot analysis and direct enzyme assay, and these plants accumulated substantially more essential oil (about 50% yield increase) without change in monoterpene composition compared with wild-type. Chlorophyll-deficient plants did not afford detectable reductoisomerase mRNA or enzyme activity and yielded less essential oil than did wild-type plants, indicating cosuppression of the reductoisomerase gene. Plants transformed with the antisense version of the menthofuran synthase cDNA were normal in appearance but produced less than half of this undesirable monoterpene oil component than did wild-type mint grown under unstressed or stressed conditions. These experiments demonstrate that essential oil quantity and quality can be regulated by metabolic engineering. Thus, alteration of the committed step of the mevalonate-independent pathway for supply of terpenoid precursors improves flux through the pathway that leads to increased monoterpene production, and antisense manipulation of a selected downstream monoterpene biosynthetic step leads to improved oil composition.

Data gathering in sensor networks using the energy*delay metric

Abstract: In this paper we consider the problem of data collection from a sensor web consisting of N nodes, where nodes have packets of data in each round of communication that need to be gathered and fused with other nodes’ packets into one packet and transmitted to a distant base station. Nodes have power control in their wireless communications and can transmit directly to any node in the network or to the base station. With unit delay cost for each packet transmission, if all nodes transmit data directly to the base station, then both high energy and high delay per round will occur. In our prior work [6], we developed an algorithm to minimize the energy cost per round, where a linear chain of all the nodes are formed to gather data, and nodes took turns to transmit to the base station. If the goal is to minimize the delay cost, then a binary combining scheme can be used to accomplish this task in about log N units of delay with parallel communications and incurring a slight increase in energy cost. The goal is to find data gathering schemes that balance the energy and delay cost, as measured by energy*delay. We conducted extensive simulation experiments with a number of schemes for this problem with 100 nodes in playing fields of 50m x 50m and 100m x 100m and the base station located at least 100 meters and 200 meters, respectively, from any node. With CDMA capable sensor nodes, a chain-based binary scheme performs best in terms of energy*delay. If the sensor nodes are not CDMA capable, then parallel communications are possible only among spatially separated nodes, and a chain-based 3 level hierarchy scheme performs well. These schemes perform 60 to 100 times better than direct scheme and also outperform a cluster based scheme, called LEACH [3].

BIOSYNTHESIS OF ASCORBIC ACID IN PLANTS: A Renaissance.

Abstract: ▪ Abstract The structure of the familiar antioxidant L-ascorbic acid (vitamin C) was described in 1933 yet remarkably, its biosynthesis in plants remained elusive until only recently. It became clear from radioisotopic labeling studies in the 1950s that plant ascorbic acid biosynthesis does not proceed in toto via a route similar to that in mammals. The description in 1996 of an Arabidopsis thaliana mutant deficient in ascorbic acid prompted renewed research effort in this area, and subsequently in 1998 a new pathway was discovered that is backed by strong biochemical and molecular genetic evidence. This pathway proceeds through the intermediates GDP-D-mannose, L-galactose, and L-galactono-1,4-lactone. Much research has focused on the properties of the terminal enzyme responsible for conversion of the aldonolactone to ascorbate, and on related enzymes in both mammals and fungi. Two of the plant biosynthetic genes have been studied at the molecular level and additional ascorbate-deficient A. thaliana mutan...

Parenting, self-control, and delinquency: a test of self-control theory*

Abstract: Self-control theory has received extensive empirical attention in the past decade, but most studies have not tested its arguments about the effects of parenting on self-control and delinquency. Using data collected from a sample of urban high school students, this study addresses this void by examining two parenting-related hypotheses derived from the theory. For one of the hypotheses, the results with self-control theory are contrasted with those obtained with Baumrind's theory of authoritative parenting, a theory that also is concerned with the link between parenting and self-control. Results generally support self-control theory's two hypotheses, but also point to empirical limitations of the theory.

Maternal androgens in black-headed gull (Larus ridibundus) eggs: consequences for chick development

Abstract: We tested the hypothesis that mother birds counterbalance the negative effects of hatching asynchrony for later–hatched chicks by increasing the yolk androgen concentrations in consecutive eggs of their clutch. In doing so, they may adaptively tune each offspring9s competitive ability and, thus, growth and survival. However, evidence in support of this hypothesis is contradictory. The yolk concentrations of maternal androgens in the eggs of black–headed gulls increase significantly with the laying order of the eggs in a clutch. We experimentally tested the functional consequences of this increase on chick development under natural conditions by injecting eggs with either an oil or androgen solution. We created experimental clutches in which androgen levels either stayed constant or increased with laying order while controlling for differences in egg quality by using only first–laid eggs. We then compared development, growth and survival between these broods. Androgen treatment enhanced embryonic development because androgen–treated eggs hatched half a day earlier than controls, while their size at hatching was similar to oil–treated controls. Androgen treatment did not increase chick survival, but it enhanced growth. Androgen–treated, third–hatched chicks had a higher body mass and longer legs than thirdndash;hatched chicks that hatched from oil–treated eggs. At the same time, growth of first chicks (which were all oil treated) was reduced by the presence of two androgen–treated siblings, suggesting that yolk androgens enhance the competitive ability of later–hatched chicks. Our results support the hypothesis that transfer of different amounts of androgens to the eggs of a clutch is a mechanism by which mothers maximize their reproductive output.

Examining the shareholder wealth effects of announcements of newly created CIO positions

Abstract: While information technology (IT) has been transforming the business landscape for a long time now, it is only recently that empirical evidence demonstrating the positive impact of IT on firm performance has begun to accumulate The strategic importance of a firm's IT capabilities is prompting an increasing number of companies to appoint chief information officers (CIOs) to effectively manage these assets Such moves are reflective of changes in top management thinking and policy regarding the role of IT and firms' approaches to IT governance This paper uses the event study methodology to examine market reactions to announcements of new CIO positions Findings strongly support the notion that, for firms competing in industries undergoing IT-driven transformation, announcements of newly created CIO positions do indeed provoke positive reactions from the marketplace

The effects of job insecurity on employee safety outcomes: cross-sectional and longitudinal explorations.

Abstract: Job insecurity research has focused primarily on attitudinal (e.g., job satisfaction), behavioral (e.g., employee turnover), and health outcomes. Moreover, research in the area of workplace safety has largely focused on ergonomic factors and personnel selection and training as primary antecedents of safety. Two cross-sectional structural equational modeling analyses and 1 longitudinal regression analysis of 237 food-processing plant employees unite these 2 disparate areas of research by exploring the relatively uncharted relationship between job insecurity and safety outcomes. Results indicate that employees who report high perceptions of job insecurity exhibit decreased safety motivation and compliance, which in turn are related to higher levels of workplace injuries and accidents. The specter of losing one's job as a result of corporate restructuring, mergers and acquisitions, or organizational downsizing looms in the foreground for many of today's employees. Fortune 500 companies alone have reduced their total workforce from an aggregate 14.1 million employees to 11.6 million between 1983 and 1993, with approximately 500,000 U.S. employees facing job loss each year as a result of these transitions (Simons, 1998). These are impressive numbers; however, they do not even begin to capture the number of employees who might be concerned about losing their own jobs or the effect job

Temperature dependence of the thermal conductivity of single-wall carbon nanotubes

Abstract: The thermal conductivity of several single-wall carbon nanotubes has been calculated over a temperature range of 100-500 K using molecular dynamics simulations with the Tersoff-Brenner potential for C-C interactions. In all cases, starting from similar values at 100 K, the thermal conductivities show a peaking behaviour before falling off at higher temperatures. The peak position shifts to higher temperatures for nanotubes with larger diameters and no significant dependence on the tube chirality is observed. It is shown that this phenomenon is due to the onset of Umklapp scattering, which shifts to higher temperatures for nanotubes with larger diameters.

RALF, a 5-kDa ubiquitous polypeptide in plants, arrests root growth and development.

Abstract: A 5-kDa polypeptide was isolated from tobacco leaves that induced a rapid alkalinization of the culture medium of tobacco suspension-cultured cells and a concomitant activation of an intracellular mitogen-activated protein kinase. An N-terminal sequence was obtained, and a cDNA coding for the 49-aa polypeptide was isolated from a tobacco cDNA library. The cDNA encoded a preproprotein of 115 amino acids that contained the polypeptide at its C terminus. A search among known expressed sequence tags revealed that genes encoding Rapid ALkalinization Factor (RALF) preproproteins were present in various tissues and organs from 16 species of plants representing 9 families. A tomato homolog of the polypeptide was synthesized and, when supplied to germinating tomato and Arabidopsis seeds, it caused an arrest of root growth and development. Although its specific role in growth has not been established, the polypeptide joins the ranks of the increasing number of polypeptide hormones that are known to regulate plant stress, growth, and development.

Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene

Abstract: A subpopulation of collie dogs is extremely sensitive to neurotoxicity induced by ivermectin. The aim of this study was to determine the mechanistic basis for this phenomenon. The multi-drug-resistance gene (mdr1) encodes a large transmembrane protein, P-glycoprotein (P-gp), that is an integral part of the blood-brain barrier. P-gp functions as a drug-transport pump at the blood-brain barrier, transporting a variety of drugs from the brain back into the blood. Since ivermectin is a substrate for P-gp, we hypothesized that ivermectin-sensitive collies had altered mdr1 expression compared with unaffected collies. We report a deletion mutation of the mdr1 gene that is associated with ivermectin sensitivity. The 4-bp deletion results in a frame shift, generating several stop codons that prematurely terminate P-gp synthesis. Dogs that are homozygous for the deletion mutation display the ivermectin-sensitive phenotype, while those that are homozygous normal or heterozygous do not display increased sensitivity to ivermectin.