Showing papers by "University of Missouri published in 2007"
TL;DR: The reported levels of BPA in human fluids are higher than the BPA concentrations reported to stimulate molecular endpoints in vitro and appear to be within an order of magnitude of the levels needed to induce effects in animal models.
2,391 citations
TL;DR: In this paper, the authors calculated IR emission spectra for dust heated by starlight, for mixtures of amorphous silicate and graphitic grains, including varying amounts of PAH particles.
Abstract: IR emission spectra are calculated for dust heated by starlight, for mixtures of amorphous silicate and graphitic grains, including varying amounts of PAH particles. The models are constrained to reproduce the average Milky Way extinction curve. The calculations include the effects of single-photon heating. Updated IR absorption properties for the PAHs are presented that are consistent with observed emission spectra, including those newly obtained by Spitzer. We find a size distribution for the PAHs giving emission band ratios consistent with the observed spectra of the Milky Way and other galaxies. Emission spectra are presented for a wide range of starlight intensities. We calculate how the efficiency of emission into different IR bands depends on PAH size; the strong 7.7 μm emission feature is produced mainly by PAH particles containing Umin. We present graphical procedures using Spitzer IRAC and MIPS photometry to estimate the parameters qPAH, Umin, and γ, the fraction fPDR of the dust luminosity coming from photodissociation regions with U > 100, and the total dust mass Mdust.
2,102 citations
TL;DR: There is an emergence of inactivity physiology studies beginning to raise a new concern with potentially major clinical and public health significance: the average nonexercising person may become even more metabolically unfit in the coming years if they sit too much, thereby limiting the normally high volume of intermittent nonexercise physical activity in everyday life.
Abstract: It is not uncommon for people to spend one-half of their waking day sitting, with relatively idle muscles. The other half of the day includes the often large volume of nonexercise physical activity. Given the increasing pace of technological change in domestic, community, and workplace environments, modern humans may still not have reached the historical pinnacle of physical inactivity, even in cohorts where people already do not perform exercise. Our purpose here is to examine the role of sedentary behaviors, especially sitting, on mortality, cardiovascular disease, type 2 diabetes, metabolic syndrome risk factors, and obesity. Recent observational epidemiological studies strongly suggest that daily sitting time or low nonexercise activity levels may have a significant direct relationship with each of these medical concerns. There is now a need for studies to differentiate between the potentially unique molecular, physiologic, and clinical effects of too much sitting (inactivity physiology) separate from the responses caused by structured exercise (exercise physiology). In theory, this may be in part because nonexercise activity thermogenesis is generally a much greater component of total energy expenditure than exercise or because any type of brief, yet frequent, muscular contraction throughout the day may be necessary to short-circuit unhealthy molecular signals causing metabolic diseases. One of the first series of controlled laboratory studies providing translational evidence for a molecular reason to maintain high levels of daily low-intensity and intermittent activity came from examinations of the cellular regulation of skeletal muscle lipoprotein lipase (LPL) (a protein important for controlling plasma triglyceride catabolism, HDL cholesterol, and other metabolic risk factors). Experimentally reducing normal spontaneous standing and ambulatory time had a much greater effect on LPL regulation than adding vigorous exercise training on top of the normal level of nonexercise activity. Those studies also found that inactivity initiated unique cellular processes that were qualitatively different from the exercise responses. In summary, there is an emergence of inactivity physiology studies. These are beginning to raise a new concern with potentially major clinical and public health significance: the average nonexercising person may become even more metabolically unfit in the coming years if they sit too much, thereby limiting the normally high volume of intermittent nonexercise physical activity in everyday life. Thus, if the inactivity physiology paradigm is proven to be true, the dire concern for the future may rest with growing numbers of people unaware of the potential insidious dangers of sitting too much and who are not taking advantage of the benefits of maintaining nonexercise activity throughout much of the day.
1,577 citations
TL;DR: In this article, the authors present an unusually comprehensive and detailed literature analysis of the stream of research on university entrepreneurship, now encompassing 173 articles published in a variety of academic journals, and inductively derive a framework describing the dynamic process of university entrepreneurship based on a synthesis of the literature.
Abstract: The literature on university entrepreneurship is rapidly expanding, in both the United States and Europe. Since the literature is also fairly fragmented, however, we submit that it is time to take stock of the current knowledge to provide directions for future research and guideposts for policy makers. To accomplish this, we present an unusually comprehensive and detailed literature analysis of the stream of research on university entrepreneurship, now encompassing 173 articles published in a variety of academic journals. Four major research streams emerge in this area of study: (i) entrepreneurial research university, (ii) productivity of technology transfer offices, (iii) new firm creation, and (iv) environmental context including networks of innovation. We inductively derive a framework describing the dynamic process of university entrepreneurship based on a synthesis of the literature. We submit that this framework is useful in guiding future research on this important, yet complex and under-researched topic.
1,456 citations
Michigan State University1, University of California, Davis2, University of California, Santa Barbara3, Grinnell College4, Florida Institute of Technology5, University of California, San Diego6, Smithsonian Institution7, Cornell University8, Academy of Natural Sciences of Drexel University9, Dartmouth College10, Yale University11, University of Chicago12, University of Missouri13, University of Georgia14, University of British Columbia15
TL;DR: Two major hypotheses for the origin of the latitudinal diversity gradient are reviewed, including the time and area hypothesis and the diversification rate hypothesis, which hold that tropical regions diversify faster due to higher rates of speciation, or due to lower extinction rates.
Abstract: A latitudinal gradient in biodiversity has existed since before the time of the dinosaurs, yet how and why this gradient arose remains unresolved. Here we review two major hypotheses for the origin of the latitudinal diversity gradient. The time and area hypothesis holds that tropical climates are older and historically larger, allowing more opportunity for diversification. This hypothesis is supported by observations that temperate taxa are often younger than, and nested within, tropical taxa, and that diversity is positively correlated with the age and area of geographical regions. The diversification rate hypothesis holds that tropical regions diversify faster due to higher rates of speciation (caused by increased opportunities for the evolution of reproductive isolation, or faster molecular evolution, or the increased importance of biotic interactions), or due to lower extinction rates. There is phylogenetic evidence for higher rates of diversification in tropical clades, and palaeontological data demonstrate higher rates of origination for tropical taxa, but mixed evidence for latitudinal differences in extinction rates. Studies of latitudinal variation in incipient speciation also suggest faster speciation in the tropics. Distinguishing the roles of history, speciation and extinction in the origin of the latitudinal gradient represents a major challenge to future research.
1,435 citations
Princeton University1, University of Wyoming2, Imperial College London3, University of Arizona4, California Institute of Technology5, University of Cambridge6, University of Missouri7, Max Planck Society8, Space Telescope Science Institute9, New York University10, Yale University11, Ames Research Center12
TL;DR: Physical dust models for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands were presented for each galaxy as discussed by the authors, estimating the total dust mass, the fraction of the dust mass contributed by PAHs, and the intensity of the starlight heating the dust grains.
Abstract: Physical dust models are presented for 65 galaxies in SINGS that are strongly detected in the four IRAC bands and three MIPS bands. For each galaxy we estimate (1) the total dust mass, (2) the fraction of the dust mass contributed by PAHs, and (3) the intensity of the starlight heating the dust grains. We find that spiral galaxies have dust properties resembling the dust in the local region of the Milky Way, with similar dust-to-gas ratio and similar PAH abundance. The observed SEDs, including galaxies with SCUBA photometry, can be reproduced by dust models that do not require "cold" (T ≾ 10 K) dust. The dust-to-gas ratio is observed to be dependent on metallicity. In the interstellar media of galaxies with A_O ≡ 12 + log_(10)(O/H) > 8.1, grains contain a substantial fraction of interstellar Mg, Si, and Fe. Galaxies with A_O 8.1 have a median q_(PAH) = 3.55%. The derived dust masses favor a value X_(CO) ≈ 4 × 10^(20) cm^(-2) (K km s^(-1))^(-1) for the CO-to-H_2 conversion factor. Except for some starbursting systems (Mrk 33, Tol 89, NGC 3049), dust in the diffuse ISM dominates the IR power.
1,108 citations
TL;DR: A 12-item, short form of the Experiences in Close Relationship Scale (ECR) was developed across 6 studies and validity found to be equivalent for the short and the original versions of the ECR across studies.
Abstract: We developed a 12-item, short form of the Experiences in Close Relationship Scale (ECR; Brennan, Clark, & Shaver, 1998) across 6 studies. In Study 1, we examined the reliability and factor structure of the measure. In Studies 2 and 3, we cross-validated the reliability, factor structure, and validity of the short form measure; whereas in Study 4, we examined test-retest reliability over a 1-month period. In Studies 5 and 6, we further assessed the reliability, factor structure, and validity of the short version of the ECR when administered as a stand-alone instrument. Confirmatory factor analyses indicated that 2 factors, labeled Anxiety and Avoidance, provided a good fit to the data after removing the influence of response sets. We found validity to be equivalent for the short and the original versions of the ECR across studies. Finally, the results were comparable when we embedded the short form within the original version of the ECR and when we administered it as a stand-alone measure.
1,077 citations
TL;DR: It is likely, but requiring further confirmation, that adult exposure to BPA affects the brain, the female reproductive system, and the immune system and that developmental effects occur in theFemale reproductive system.
1,065 citations
University of Massachusetts Amherst1, Space Telescope Science Institute2, University of Cambridge3, University of Arizona4, Princeton University5, University of Hawaii at Manoa6, New York University7, University of Wyoming8, California Institute of Technology9, Ames Research Center10, Imperial College London11, University of Missouri12, Yale University13, Max Planck Society14, Bucknell University15
TL;DR: In this paper, the authors analyzed Spitzer 8 and 24 μm data of star-forming regions in a sample of 33 nearby galaxies with available HST NICMOS images in the Paα (1.8756 μm) emission line.
Abstract: With the goal of investigating the degree to which the MIR emission traces the SFR, we analyze Spitzer 8 and 24 μm data of star-forming regions in a sample of 33 nearby galaxies with available HST NICMOS images in the Paα (1.8756 μm) emission line. The galaxies are drawn from the SINGS sample and cover a range of morphologies and a factor ~10 in oxygen abundance. Published data on local low-metallicity starburst galaxies and LIRGs are also included in the analysis. Both the stellar continuum-subtracted 8 μm emission and the 24 μm emission correlate with the extinction-corrected Paα line emission, although neither relationship is linear. Simple models of stellar populations and dust extinction and emission are able to reproduce the observed nonlinear trend of the 24 μm emission versus number of ionizing photons, including the modest deficiency of 24 μm emission in the low-metallicity regions, which results from a combination of decreasing dust opacity and dust temperature at low luminosities. Conversely, the trend of the 8 μm emission as a function of the number of ionizing photons is not well reproduced by the same models. The 8 μm emission is contributed, in larger measure than the 24 μm emission, by dust heated by nonionizing stellar populations, in addition to the ionizing ones, in agreement with previous findings. Two SFR calibrations, one using the 24 μm emission and the other using a combination of the 24 μm and Hα luminosities (Kennicutt and coworkers), are presented. No calibration is presented for the 8 μm emission because of its significant dependence on both metallicity and environment. The calibrations presented here should be directly applicable to systems dominated by ongoing star formation.
1,032 citations
TL;DR: Serk3/BAK1 appears to integrate diverse perception events into downstream PAMP responses, leading to immunity against a range of invading microbes.
Abstract: In pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI), plant cell surface receptors sense potential microbial pathogens by recognizing elicitors called PAMPs. Although diverse PAMPs trigger PTI through distinct receptors, the resulting intracellular responses overlap extensively. Despite this, a common component(s) linking signal perception with transduction remains unknown. In this study, we identify SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK)3/brassinosteroid-associated kinase (BAK)1, a receptor-like kinase previously implicated in hormone signaling, as a component of plant PTI. In Arabidopsis thaliana, AtSERK3/BAK1 rapidly enters an elicitor-dependent complex with FLAGELLIN SENSING 2 (FLS2), the receptor for the bacterial PAMP flagellin and its peptide derivative flg22. In the absence of AtSERK3/BAK1, early flg22-dependent responses are greatly reduced in both A. thaliana and Nicotiana benthamiana. Furthermore, N. benthamiana Serk3/Bak1 is required for full responses to unrelated PAMPs and, importantly, for restriction of bacterial and oomycete infections. Thus, SERK3/BAK1 appears to integrate diverse perception events into downstream PAMP responses, leading to immunity against a range of invading microbes.
1,032 citations
University of Arizona1, Princeton University2, University of Wyoming3, University of Cambridge4, California Institute of Technology5, Max Planck Society6, Imperial College London7, Space Telescope Science Institute8, Ames Research Center9, University of Missouri10, Arizona State University11, Yale University12
TL;DR: In this article, a sample of low-resolution 5-38 μm Spitzer IRS spectra of the inner few square kiloparsecs of 59 nearby galaxies spanning a large range of star formation properties was used to explore the behavior of PAH emission and the prevalence of silicate dust extinction.
Abstract: We present a sample of low-resolution 5-38 μm Spitzer IRS spectra of the inner few square kiloparsecs of 59 nearby galaxies spanning a large range of star formation properties. A robust method for decomposing mid-infrared galaxy spectra is described and used to explore the behavior of PAH emission and the prevalence of silicate dust extinction. Evidence for silicate extinction is found in ~1/8 of the sample, at strengths that indicate that most normal galaxies undergo A_V ≲ 3 mag averaged over their centers. The contribution of PAH emission to the total infrared power is found to peak near 10% and extend up to ~20% and is suppressed at metallicities Z ≲ Z_☉/4, as well as in low-luminosity AGN environments. Strong interband PAH feature strength variations (2-5 times) are observed, with the presence of a weak AGN and, to a lesser degree, increasing metallicity shifting power to the longer wavelength bands. A peculiar PAH emission spectrum with markedly diminished 5-8 μm features arises among the sample solely in systems with relatively hard radiation fields harboring low-luminosity AGNs. The AGNs may modify the emitting grain distribution and provide the direct excitation source of the unusual PAH emission, which cautions against using absolute PAH strength to estimate star formation rates in systems harboring active nuclei. Alternatively, the low star formation intensity often associated with weak AGNs may affect the spectrum. The effect of variations in the mid-infrared spectrum on broadband infrared surveys is modeled and points to more than a factor of 2 uncertainty in results that assume a fixed PAH emission spectrum, for redshifts z = 0-2.5.
TL;DR: It is concluded that early experience, biological factors, educational policy, and cultural context affect the number of women and men who pursue advanced study in science and math and that these effects add and interact in complex ways.
Abstract: SUMMARY—Amid ongoing public speculation about the reasons for sex differences in careers in science and mathematics, we present a consensus statement that is based on the best available scientific evidence. Sex differences in science and math achievement and ability are smaller for the mid-range of the abilities distribution than they are for those with the highest levels of achievement and ability. Males are more variable on most measures of quantitative and visuospatial ability, which necessarily results in more males at both high- and low-ability extremes; the reasons why males are often more variable remain elusive. Successful careers in math and science require many types of cognitive abilities. Females tend to excel in verbal abilities, with large differences between females andmalesfound whenassessmentsincludewriting samples. High-level achievement in science and math requires the ability to communicate effectively and comprehend abstract ideas, so the female advantage in writing should be helpful in all academic domains. Males outperform females on most measures of visuospatial abilities, which have been implicated as contributing to sex differences on standardized examsin mathematics and science. An evolutionary account of sex differences in mathematics and science supports the conclusion that, although sex differences in math and science performance have not directly evolved, they could be indirectly related to differences in interests and specific brain and cognitive systems. We review the brain basis for sex differences in science and mathematics, describe consistent effects, and identify numerous possible correlates. Experience alters brain structures and functioning, so causal statements about brain differences and success in math and science are circular. A wide range of sociocultural forces contribute to sex differences in mathematics and science achievement and ability—including the effects of family,neighborhood,peer,andschoolinfluences;training and experience; and cultural practices. We conclude that early experience, biological factors, educational policy, and cultural context affect the number of women and men who pursue advanced study in science and math and that these effects add and interact in complex ways. There are no single or simple answers to the complex questions about sex differences in science and mathematics.
TL;DR: Recent advances have provided information on regulation of ARF gene expression, ARF roles in growth and developmental processes, and target genes regulated by ARFs.
TL;DR: It may be time to consider a shift to a dimensional classification of personality disorder that would help address the failures of the existing diagnostic categories as well as contribute to an integration of the psychiatric diagnostic manual with psychology's research on general personality structure.
Abstract: The diagnostic categories of the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders were developed in the spirit of a traditional medical model that considers mental disorders to be qualitatively distinct conditions (see, e.g., American Psychiatric Association, 2000). Work is now beginning on the fifth edition of this influential diagnostic manual. It is perhaps time to consider a fundamental shift in how psychopathology is conceptualized and diagnosed. More specifically, it may be time to consider a shift to a dimensional classification of personality disorder that would help address the failures of the existing diagnostic categories as well as contribute to an integration of the psychiatric diagnostic manual with psychology's research on general personality structure.
TL;DR: The longitudinal finding that the strength of the association is stronger when personal well-being is treated as the dependent variable supports previous theorizing and suggests that longitudinal effects are more likely to be uncovered when using standard measurement.
Abstract: This study examines the association between marital quality and personal well-being using meta-analytic techniques. Effects from 93 studies were analyzed. The average weighted effect size r was .37 for cross-sectional and .25 for longitudinal effects. Results indicate that several variables moderate the association between marital quality and personal well-being, including gender, participants’ marital duration, source of measurement, data collection year, and dependent variable. These results suggest that longitudinal effects are more likely to be uncovered when using standard measurement and that future research should use samples homogenous in marital length. The longitudinal finding that the strength of the association is stronger when personal well-being is treated as the dependent variable supports previous theorizing.
TL;DR: The children with MLD showed deficits across all math cognition tasks, many of which were partially or fully mediated by working memory or speed of processing.
Abstract: Using strict and lenient mathematics achievement cutoff scores to define a learning disability, respective groups of children who are math disabled (MLD, n = 15) and low achieving (LA, n = 44) were identified. These groups and a group of typically achieving (TA, n = 46) children were administered a battery of mathematical cognition, working memory, and speed of processing measures (M = 6 years). The children with MLD showed deficits across all math cognition tasks, many of which were partially or fully mediated by working memory or speed of processing. Compared with the TA group, the LA children were less fluent in processing numerical information and knew fewer addition facts. Implications for defining MLD and identifying underlying cognitive deficits are discussed.
TL;DR: In 2 time-lagged samples, the authors found that motivation mediates the emotional exhaustion-job performance relationship and participants appear to target their investment of resources in response to emotional exhaustion to develop social support through social exchange.
Abstract: The literature concerning the relationship between emotional exhaustion and performance led researchers to raise questions about the extent to which the variables are related. In 2 time-lagged samples, the authors found that motivation mediates the emotional exhaustion-job performance relationship. Moreover, the authors found that participants appear to target their investment of resources in response to emotional exhaustion to develop social support through social exchange; specifically, emotional exhaustion was associated with communion striving resources that were manifest in the form of organizational citizenship behaviors targeted at individuals. Implications of this relationship for theories of burnout and for management practice are discussed.
TL;DR: In this article, the authors examined associations between undergraduate students' sense of class belonging and their academic motivation in that class, their sense of self-efficacy, intrinsic motivation, and task value.
Abstract: The importance of students' sense of school belonging for many adaptive outcomes is becoming well established; however, few researchers have focused on college-aged populations. In this study, the authors examined associations between undergraduate students' sense of class belonging and their academic motivation in that class, their sense of class belonging and perceptions of their instructors' characteristics, and their class and campus-level sense of belonging. They distributed questionnaires to students at a southeastern university; freshmen (N = 238) completed the questionnaire. The authors found associations between (a) students' sense of class belonging and their academic self-efficacy, intrinsic motivation, and task value; (b) students' sense of class-level belonging and their perceptions of instructors' warmth and openness, encouragement of student participation, and organization; and (c) students' sense of university-level belonging and their sense of social acceptance. The authors found smaller ...
TL;DR: It is reported that Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6, two environmentally responsive mitogen-activated protein kinases (MAPK) and their upstream MAPK kinases, MKK4 and MKK5, are key regulators of stomatal development and patterning.
Abstract: Stomata are specialized epidermal structures that regulate gas (CO2 and O2) and water vapor exchange between plants and their environment. In Arabidopsis thaliana, stomatal development is preceded by asymmetric cell divisions, and stomatal distribution follows the one-cell spacing rule, reflecting the coordination of cell fate specification. Stomatal development and patterning are regulated by both genetic and environmental signals. Here, we report that Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3 (MPK3) and MPK6, two environmentally responsive mitogen-activated protein kinases (MAPKs), and their upstream MAPK kinases, MKK4 and MKK5, are key regulators of stomatal development and patterning. Loss of function of MKK4/MKK5 or MPK3/MPK6 disrupts the coordinated cell fate specification of stomata versus pavement cells, resulting in the formation of clustered stomata. Conversely, activation of MKK4/MKK5-MPK3/MPK6 causes the suppression of asymmetric cell divisions and stomatal cell fate specification, resulting in a lack of stomatal differentiation. We further establish that the MKK4/MKK5-MPK3/MPK6 module is downstream of YODA, a MAPKKK. The establishment of a complete MAPK signaling cascade as a key regulator of stomatal development and patterning advances our understanding of the regulatory mechanisms of intercellular signaling events that coordinate cell fate specification during stomatal development.
University of Missouri1, Auburn University2, University of Cincinnati3, United States Environmental Protection Agency4, Maryville College5, University of Siena6, University of Florida7, Harvard University8, National Institutes of Health9, Washington State University10, National Institutes of Natural Sciences, Japan11, Brunel University London12, Case Western Reserve University13, University of Connecticut14, North Carolina State University15, Emory University16, Tulane University17, Universidad Miguel Hernández de Elche18, University of Granada19, University of Illinois at Chicago20, United States Geological Survey21, Tufts University22, Charité23, Carleton College24, University of Texas Medical Branch25, University of Massachusetts Amherst26
TL;DR: This document is a summary statement of the outcome from he meeting: “Bisphenol A: An Examination of the Relevance of cological, In vitro and Laboratory Animal Studies for Assessng Risks to Human Health” sponsored by both the NIEHS and IDCR at NIH/DHHS.
TL;DR: It is emphasized that adolescent alcohol use primarily takes place in a social context, and that therefore studies should not solely focus on intra-individual factors predicting substance use and misuse but also on interpersonal social factors.
Abstract: This paper presents a review and a model of the development of addictive behaviors in (human) adolescents, with a focus on alcohol. The model proposes that addictive behaviors develop as the result of an imbalance between two systems: an appetitive, approach-oriented system that becomes sensitized with repeated alcohol use and a regulatory executive system that is not fully developed and that is compromised by exposure to alcohol. Self-regulation critically depends on two factors: ability and motivation to regulate the appetitive response tendency. The motivational aspect is often still weak in heavy drinking adolescents, who typically do not recognize their drinking as problematic. Motivation to regulate use often develops only years later, after the individual has encountered serious alcohol-related problems. Unfortunately, at that point behavioral change becomes harder due to several neurocognitive adaptations that result from heavy drinking. As we document, there is preliminary support for the central elements of the model (appetitive motivation vs. self-regulation), but there is a paucity of research directly addressing these mechanisms in human adolescents. Further, we emphasize that adolescent alcohol use primarily takes place in a social context, and that therefore studies should not solely focus on intra-individual factors predicting substance use and misuse but also on interpersonal social factors. Finally, we discuss implications of the model for interventions.
TL;DR: The Vroom, Yetton, and Jago contingency models of participation in decision making are described in depth, and their work provides the basis for identifying 3 distinct ways in which situational or contextual variables are relevant to both research on and the practice of leadership.
Abstract: Leadership depends on the situation. Few social scientists would dispute the validity of this statement. But the statement can be interpreted in many different ways, depending, at least in part, on what one means by leadership. This article begins with a definition of leadership and a brief description of 3 historically important theories of leadership. The most recent of these, contingency theories, is argued to be most consistent with existing evidence and most relevant to professional practice. The Vroom, Yetton, and Jago contingency models of participation in decision making are described in depth, and their work provides the basis for identifying 3 distinct ways in which situational or contextual variables are relevant to both research on and the practice of leadership.
TL;DR: Genetic, epigenetic, gene expression, and phenotypic changes in ∼50 resynthesized Brassica napus lines independently derived by hybridizing double haploids of Brassica oleracea and Brassica rapa indicate that exchanges among homoeologous chromosomes are a major mechanism creating novel allele combinations and phenotypesic variation in newly formed B. napus polyploids.
Abstract: Many previous studies have provided evidence for genome changes in polyploids, but there are little data on the overall population dynamics of genome change and whether it causes phenotypic variability. We analyzed genetic, epigenetic, gene expression, and phenotypic changes in ∼50 resynthesized Brassica napus lines independently derived by hybridizing double haploids of Brassica oleracea and Brassica rapa. A previous analysis of the first generation (S0) found that genetic changes were rare, and cytosine methylation changes were frequent. Our analysis of a later generation found that most S0 methylation changes remained fixed in their S5 progeny, although there were some reversions and new methylation changes. Genetic changes were much more frequent in the S5 generation, occurring in every line with lines normally distributed for number of changes. Genetic changes were detected on 36 of the 38 chromosomes of the S5 allopolyploids and were not random across the genome. DNA fragment losses within lines often occurred at linked marker loci, and most fragment losses co-occurred with intensification of signal from homoeologous markers, indicating that the changes were due to homoeologous nonreciprocal transpositions (HNRTs). HNRTs between chromosomes A1 and C1 initiated in early generations, occurred in successive generations, and segregated, consistent with a recombination mechanism. HNRTs and deletions were correlated with qualitative changes in the expression of specific homoeologous genes and anonymous cDNA amplified fragment length polymorphisms and with phenotypic variation among S5 polyploids. Our data indicate that exchanges among homoeologous chromosomes are a major mechanism creating novel allele combinations and phenotypic variation in newly formed B. napus polyploids.
TL;DR: It is shown by complete genome sequencing of two symbiotic, photosynthetic, Bradyrhizobium strains, BTAi1 and ORS278, that canonical nodABC genes and typical lipochito-oligosaccharidic Nod factors are not required for symbiosis in some legumes.
Abstract: Leguminous plants (such as peas and soybeans) and rhizobial soil bacteria are symbiotic partners that communicate through molecular signaling pathways, resulting in the formation of nodules on legume roots and occasionally stems that house nitrogen-fixing bacteria. Nodule formation has been assumed to be exclusively initiated by the binding of bacterial, host-specific lipochito-oligosaccharidic Nod factors, encoded by the nodABC genes, to kinase-like receptors of the plant. Here we show by complete genome sequencing of two symbiotic, photosynthetic, Bradyrhizobium strains, BTAi1 and ORS278, that canonical nodABC genes and typical lipochito-oligosaccharidic Nod factors are not required for symbiosis in some legumes. Mutational analyses indicated that these unique rhizobia use an alternative pathway to initiate symbioses, where a purine derivative may play a key role in triggering nodule formation.
TL;DR: Factor analyses indicated that lack of planning and lack of persistence are two distinct facets of one broader trait, whereas urgency and sensation seeking are both very modestly related to each other and to the planning/persistence measures.
Abstract: The ability to make precise distinctions among related personality constructs helps clarify theory and increases the utility of clinical assessment. In three studies, the authors evaluated the validity of distinctions among four impulsivity-like traits: sensation seeking, lack of planning, lack of persistence, and urgency (acting rashly when distressed). Factor analyses indicated that lack of planning and lack of persistence are two distinct facets of one broader trait, whereas urgency and sensation seeking are both very modestly related to each other and to the planning/persistence measures. The authors developed interview assessments of each, and multitrait, multimethod matrix results indicated clear convergent and discriminant validity among the constructs. The distinctions among them were useful: The traits accounted for different aspects of risky behaviors. Sensation seeking appeared to relate to the frequency of engaging in risky behaviors, and urgency appeared to relate to problem levels of involve...
TL;DR: Functional biomechanical properties of periostin null skin specimens and atrioventricular valve explant experiments provided direct evidence of the role that periastin plays in regulating the viscoelastic properties of connective tissues.
Abstract: Periostin is predominantly expressed in collagen-rich fibrous connective tissues that are subjected to constant mechanical stresses including: heart valves, tendons, perichondrium, cornea, and the periodontal ligament (PDL) Based on these data we hypothesize that periostin can regulate collagen I fibrillogenesis and thereby affect the biomechanical properties of connective tissues Immunoprecipitation and immunogold transmission electron microscopy experiments demonstrate that periostin is capable of directly interacting with collagen I To analyze the potential role of periostin in collagen I fibrillogenesis, gene targeted mice were generated Transmission electron microscopy and morphometric analyses demonstrated reduced collagen fibril diameters in skin dermis of periostin knockout mice, an indication of aberrant collagen I fibrillogenesis In addition, differential scanning calorimetry (DSC) demonstrated a lower collagen denaturing temperature in periostin knockout mice, reflecting a reduced level of collagen cross-linking Functional biomechanical properties of periostin null skin specimens and atrioventricular (AV) valve explant experiments provided direct evidence of the role that periostin plays in regulating the viscoelastic properties of connective tissues Collectively, these data demonstrate for the first time that periostin can regulate collagen I fibrillogenesis and thereby serves as an important mediator of the biomechanical properties of fibrous connective tissues
TL;DR: In this article, a study of 362 buyer-salesperson dyads using triadic data (from buyer, salesperson, and sales manager) examined both a customer's overall loyalty to the selling firm and the customer's loyalty vested specifically in his or her salesperson.
Abstract: In a study of 362 buyer–salesperson dyads using triadic data (from buyer, salesperson, and sales manager), the authors examine both a customer's overall loyalty to the selling firm and the customer's loyalty vested specifically in his or her salesperson. They find that only salesperson-owned loyalty, a newly identified construct, directly affects the more tangible seller financial outcomes of sales growth and selling effectiveness, whereas both salesperson-owned loyalty and loyalty to the selling firm increase the customer's willingness to pay a price premium. A longitudinal study verifies that the positive effect of salesperson-owned loyalty on sales growth persists over time. However, because salesperson-owned loyalty simultaneously increases the seller's risk of losing business if the salesperson defects to a competitor, managers need to manage effectively the benefit–risk trade-off. Increasing relationship-enhancing activities and value received by the customer builds both salesperson-owned l...
TL;DR: In this paper, it was shown that FRD3 effluxes citrate into the root vasculature, a process important for the translocation of iron to the leaves, as well as confirm previous reports suggesting that iron moves through the xylem as a ferric-citrate complex.
Abstract: Iron, despite being an essential micronutrient, becomes toxic if present at high levels. As a result, plants possess carefully regulated mechanisms to acquire iron from the soil. The ferric reductase defective3 (frd3) mutant of Arabidopsis (Arabidopsis thaliana) is chlorotic and exhibits constitutive expression of its iron uptake responses. Consequently, frd3 mutants overaccumulate iron; yet, paradoxically, the frd3 phenotypes are due to a reduction in the amount of iron present inside frd3 leaf cells. The FRD3 protein belongs to the multidrug and toxin efflux family, members of which are known to export low-Mr organic molecules. We therefore hypothesized that FRD3 loads an iron chelator necessary for the correct distribution of iron throughout the plant into the xylem. One such potential chelator is citrate. Xylem exudate from frd3 plants contains significantly less citrate and iron than the exudate from wild-type plants. Additionally, supplementation of growth media with citrate rescues the frd3 phenotypes. The ectopic expression of FRD3-GFP results in enhanced tolerance to aluminum in Arabidopsis roots, a hallmark of organic acid exudation. Consistent with this result, approximately 3 times more citrate was detected in root exudate from plants ectopically expressing FRD3-GFP. Finally, heterologous studies in Xenopus laevis oocytes reveal that FRD3 mediates the transport of citrate. These results all strongly support the hypothesis that FRD3 effluxes citrate into the root vasculature, a process important for the translocation of iron to the leaves, as well as confirm previous reports suggesting that iron moves through the xylem as a ferric-citrate complex. Our results provide additional answers to long-standing questions about iron chelation in the vasculature and organic acid transport.
TL;DR: Arginase represents a promising novel therapeutic target that may reverse endothelial and smooth muscle cell dysfunction and prevent vascular disease.
Abstract: 1. Arginase is the focal enzyme of the urea cycle hydrolysing L-arginine to urea and L-ornithine. Emerging studies have identified arginase in the vasculature and have implicated this enzyme in the regulation of nitric oxide (NO) synthesis and the development of vascular disease. 2. Arginase inhibits the production of NO via several potential mechanisms, including competition with NO synthase (NOS) for the substrate L-arginine, uncoupling of NOS resulting in the generation of the NO scavenger, superoxide and peroxynitrite, repression of the translation and stability of inducible NOS protein, inhibition of inducible NOS activity via the generation of urea and by sensitization of NOS to its endogenous inhibitor asymmetric dimethyl-L-arginine. 3. Upregulation of arginase inhibits endothelial NOS-mediated NO synthesis and may contribute to endothelial dysfunction in hypertension, ageing, ischaemia-reperfusion and diabetes. 4. Arginase also redirects the metabolism of L-arginine to L-ornithine and the formation of polyamines and L-proline, which are essential for smooth muscle cell growth and collagen synthesis. Therefore, the induction of arginase may also promote aberrant vessel wall remodelling and neointima formation. 5. Arginase represents a promising novel therapeutic target that may reverse endothelial and smooth muscle cell dysfunction and prevent vascular disease.
TL;DR: Molecular rotors are emerging as new biosensors for both bulk and local microviscosity, and for flow and fluid shear stress on a microscopic scale and with real-time response.
Abstract: Viscosity is a measure of the resistance of a fluid against gradients in flow (shear rate). Both flow and viscosity play an important role in all biological systems from the microscopic (e.g., cellular) to the systemic level. Many methods to measure viscosity and flow have drawbacks, such as the tedious and time-consuming measurement process, expensive instrumentation, or the restriction to bulk sample sizes. Fluorescent environment-sensitive dyes are known to show high sensitivity and high spatial and temporal resolution. Molecular rotors are a group of fluorescent molecules that form twisted intramolecular charge transfer (TICT) states upon photoexcitation and therefore exhibit two competing deexcitation pathways: fluorescence emission and non-radiative deexcitation from the TICT state. Since TICT formation is viscosity-dependent, the emission intensity of molecular rotors depends on the solvent's viscosity. Furthermore, shear-stress dependency of the emission intensity was recently described. Although the photophysical processes are widely explored, the practical application of molecular rotors as sensors for viscosity and the fluid flow introduce additional challenges. Intensity-based measurements are influenced by fluid optical properties and dye concentration, and solvent–dye interaction requires calibration of the measurement system to a specific solvent. Ratiometric dyes and measurement systems help solve these challenges. In addition, the combination of molecular rotors with specific recognition groups allows them to target specific sites, for example the cell membrane or cytoplasm. Molecular rotors are therefore emerging as new biosensors for both bulk and local microviscosity, and for flow and fluid shear stress on a microscopic scale and with real-time response.