Leptin prevents insulin resistance induced by conjugated linoleic acid in obese mice

Conjugated linoleic acid (CLA) reduces adipose mass and enhances insulin sensitivity in several animal models. Conversely, in some rodent models, CLA induces lipodystrophy, insulin resistance, and reduces adipokines. Leptin is an insulin sensitizing adipokine that may work by suppressing steatosis in liver and muscle, a condition that may contribute to insulin resistance. Therefore, we hypothesize that leptin prevents CLA-induced insulin resistance in obese mice by attenuating steatosis. In a 2x2 factorial design, 6-week old, male ob/ob mice were fed either a control diet or a diet supplemented with 1.5% mixed isomer CLA and received daily intraperitoneal injections of either PBS or 1.0 mg/kg leptin for 4 weeks. CLA and leptin alone or in combination decreased weight gain, which was reflected by a reduction of epididymal fat mass. At 2 and 4 weeks of feeding, leptin significantly attenuated CLA-induced increased fasting glucose, and at 4 weeks, leptin prevented CLA-induced insulin resistance. Although CLA alone significantly increased fasting insulin, leptin reduced fasting insulin levels in both diet groups. CLA significantly reduced serum adiponectin, regardless of leptin treatment. Liver and muscle triglycerides (TG) were not altered by CLA alone; however, leptin reduced liver and muscle TG in both diet groups. Fatty acid synthase mRNA, a marker of lipid synthesis was decreased by leptin, regardless of diet, but CPT-1, a marker of lipid oxidation, was not changed. These data suggest that restoration of insulin sensitivity by leptin may partially be attributed to the reduction of hepatic steatosis and by compensating for the reduction of adiponectin

The Dynamics of Political Participation: An Analysis of the Dynamic Interaction between Individuals and their Political Micro-Environment

While political choices are rarely isolated or simultaneous, the vast majority of empirical models in political science assume they are. This dissertation examines the dynamic interactions over time between individuals and their micro-environment, in which a single factor both influences, and is influenced by, the act of voting. These dynamic interactions occur in a surprisingly broad swathe of the current literature on American voting behavior, as implicit but unexamined elements of four major research traditions. When these interactions are present, they establish feedback cycles that pose both theoretical and statistical challenges if not analyzed appropriately. Researchers ignoring these cycles tend to underestimate long term influences on voting behavior, make unrealistic assumptions about changes in voting behavior over time, and produce biased results under certain conditions. I propose a methodology that can successfully identify and model these interactions: employing simulation models to represent dynamic interactions in an intuitive format, and using optimization techniques to conduct parameter estimation and hypothesis testing against empirical data. To guide the development of these simulation models, I outline a theoretical framework of the major pathways by which dynamic interactions can influence voting behavior. I then present two applications of this methodology, to study the dynamic impacts on voting of political mobilization, and of social conformity over time. In both cases, the models receive strong statistical support, in benchmark tests against existing econometric models and against empirical data on voting behavior. Both mobilization and social conformity have unstudied indirect impacts that can lead to an additional 1.7% to 4% increase in voter turnout beyond existing models. Targeted use of peer pressure can lead to even more significant increases in turnout - up to a 30% increase among otherwise indecisive voters. In the long term, targeted mobilization can create cadres of repeatedly-mobilized activists, which raises questions about whether political campaigns effectively use their mobilization funds to build their parties in the long term. These two simulation models also provide a foundation for a host of new research questions, ranging from the impact of high-intensity get-out-the-vote drives on future mobilization efforts, to the effects of an aging population on turnout behavior over time

The inheritance of resistance to stem canker in soybeans

The fungus, Diaporthe phaseolorum (Cke. and Ell.) Sacc. war. caulivora Athow and Caldwell is the causal agent of the stem canker disease in soybeans [Glycine max (L.) Merr.]. Soybean yield losses up to 80& or more in areas of the southeastern United States during the early 1980s prompted the urgency of determining the inheritance of resistance in order to facilitate development of new varieties with resistance to the pathogen. The objectives of this study were to: (1) compare the relative virulence of two stem canker isolates from Mississippi and two from Tennessee, (2) determine the inheritance of resistance to stem canker among ‘Bay,’ ‘Tracy-M,’ ‘Bragg’ and ‘J77-339’ soybean varieties, and (3) determine if the gene(s) conditioning resistance is the same in the varieties Bay and Tracy-M. All possible crosses, including reciprocals were made among the resistant parents, Bay and Tracy-M and the susceptible parents, Bragg and J77-339. During 1984 and 1985, the selfs, F1, F2, BC1 and BC2 plants of each cross were tested for their reaction to inoculation with the stem canker pathogen under greenhouse conditions. The Tennessee isolate, labeled FP3, was determined the most virulent from the greenhouse tests conducted with the four isolates. Thus, the FP3 isolate was the only isolate used for testing the selfs, F1, F2, BC1 and BC2 populations from each cross combination. Resistance to stem canker in the four soybean varieties is likely conditioned in the following ways: (1) Bay has a single dominant gene (R1R1r2r2), Tracy-M has two dominant, genes (R1R1R2R2), (3) Bragg is segregating for the R2 gene (r1r1R2~~) and, (4) J77-339 is homozygous recessive for both genes (r1r1r2r2). The single dominant gene present in Bay appears to be the same as one of the dominant genes in Tracy-M. The high level of resistance in Bay and the low level of resistance in Bradd indicates that the R1 gene confers more resistance than the R2 gene

Evolving concepts of lunar architecture: The potential of subselene development

In view of the superior environmental and operational conditions that are thought to exist in lava tubes, popular visions of permanent settlements built upon the lunar surface may prove to be entirely romantic. The factors that will ultimately come together to determine the design of a lunar base are complex and interrelated, and they call for a radical architectural solution. Whether lunar surface-deployed superstructures can answer these issues is called into question. One particularly troublesome concern in any lunar base design is the need for vast amounts of space, and the ability of man-made structures to provide such volumes in a reliable pressurized habitat is doubtful. An examination of several key environmental design issues suggests that the alternative mode of subselene development may offer the best opportunity for an enduring and humane settlement

Source of the Bursty Bulk Flow Diffuse Aurora: Electrostatic Cyclotron Harmonic and Whistler Waves in the Coupling of Bursty Bulk Flows to Auroral Precipitation

Electron cyclotron harmonic (ECH) and whistler chorus waves are recognized as the two mechanisms responsible for the resonant waveparticle interactions necessary to precipitate plasma sheet electrons into the ionosphere, producing the diffuse Aurora. Previous work has demonstrated ECH waves dominate electron scattering at L shells >8, while whistler chorus dominates scattering at L shells L 1, consistent with electron betatron acceleration. Here, however, we nd whistler chorus emissions throughout an interval of fast ows where Te,/Te,||< 1. Parallel electron beams account for the enhanced parallel electron temperature and serve as the instability mechanism for the whistler chorus. The parallel electron beams and associated cigarshaped distributions are consistent with Fermi acceleration at dipolarizations in fast ows. We demonstrate that the scattering efciency of the whistler chorus exceeds that of ECH waves, which THEMIS also detects during the fast ows. The obliquity of the whistler waves permits efcient scattering of lowerenergy electrons into the diffuse aurora. We conclude that Fermi acceleration of electrons provides one important freeenergy source for the waveparticle interactions responsible for coupling plasma sheet electrons into the diffuse aurora during substorm conditions

Evolution and Expression of MYB Genes in Diploid and Polyploid Cotton

R2R3-MYB transcription factors have been implicated in a diversity of plant-specific processes. Among the functions attributed to myb factors is the determination of cell shape, including regulation of trichome length and density. Because myb transcription factors are likely to play a role in cotton fiber development, the molecular evolutionary properties of six MYB genes previously shown to be expressed in cotton fiber initiation were examined. In accordance with their presumed central role, each of the genes display conservative substitution patterns and limited sequence divergence in diploid members of the genus Gossypium, and this pattern is conserved in allotetraploid cottons. In contrast to highly reiterated rDNA repeats, GhMYB homologues (duplicated gene pairs) exhibit no evidence of concerted evolution, but instead appear to evolve independently in the allopolyploid nucleus. Expression patterns for the MYB genes were examined in several organs to determine if there have been changes in expression patterns between the diploids (G. raimondii and G. arboreum) and the tetraploid (G. hirsutum) or between the duplicated copies in the tetraploid. Spatial and temporal expression patterns appear to have been evolutionarily conserved, both during divergence of the diploid parents of allopolyploid cotton and following polyploid formation. However, the duplicated copies of MYB1 in the tetraploid are not expressed at equal levels or equivalently in all organs, suggesting possible functional differentiation

Genomic expression dominance in allopolyploids

<p>Abstract</p> <p>Background</p> <p>Allopolyploid speciation requires rapid evolutionary reconciliation of two diverged genomes and gene regulatory networks. Here we describe global patterns of gene expression accompanying genomic merger and doubling in inter-specific crosses in the cotton genus (<it>Gossypium </it>L.).</p> <p>Results</p> <p>Employing a micro-array platform designed against 40,430 unigenes, we assayed gene expression in two sets of parental diploids and their colchicine-doubled allopolyploid derivatives. Up to half of all genes were differentially expressed among diploids, a striking level of expression evolution among congeners. In the allopolyploids, most genes were expressed at mid-parent levels, but this was achieved via a phenomenon of genome-wide expression dominance, whereby gene expression was either up- or down-regulated to the level of one of the two parents, independent of the magnitude of gene expression. This massive expression dominance was approximately equal with respect to direction (up- or down-regulation), and the same diploid parent could be either the dominant or the recessive genome depending on the specific genomic combination. Transgressive up- and down-regulation were also common in the allopolyploids, both for genes equivalently or differentially expressed between the parents.</p> <p>Conclusion</p> <p>Our data provide novel insights into the architecture of gene expression in the allopolyploid nucleus, raise questions regarding the responsible underlying mechanisms of genome dominance, and provide clues into the enigma of the evolutionary prevalence of allopolyploids.</p

Prognostic factors for musculoskeletal sickness absence and return to work among welders and metal workers

OBJECTIVES: To analyse factors that determine the occurrence of sickness absence due to musculoskeletal problems and the time it takes to return to work. METHODS: A longitudinal study with two year follow up was conducted among 283 male welders and metal workers. The survey started with a standardised interview on the occurrence of musculoskeletal complaints. 61 (22%) workers were lost to follow up. Data on sickness absence among 222 workers during the follow up were collected from absence records and self reports. Regression analysis based on proportional hazards models was applied to identify risk factors for the occurrence and duration of sickness absence due to various musculoskeletal complaints. RESULTS: During the follow up 51% of the workers attributed at least one period of sickness absence to musculoskeletal complaints which accounted for 44% of all work days lost. A history of back pain was not associated with sickness absence for back pain, partly because subjects with back pain were more likely to be lost to follow up. Neck or shoulder pain and pain of the upper extremities contributed significantly to neck or shoulder absence (relative risk (RR) 3.35; 95% confidence interval (95% CI) 1.73 to 6.47) and to upper extremities absence (RR 2.29; 95% CI 1.17 to 4.46), respectively. Company and job title were also significant predictors for sickness absence due to these musculoskeletal complaints. Absence with musculoskeletal complaints was not associated with age, height, body mass index, smoking, and duration of employment. Return to work after neck or shoulder absence was worse among metal workers than welders (RR 2.12; 95% CI 1.08 to 4.17). Return to work after lower extremities absence was strongly influenced by visiting a physician (RR 11.31; 95% CI 2.94 to 43.46) and by musculoskeletal comorbidity (RR 2.81; 95% CI 1.18 to 6.73). CONCLUSIONS: Complaints of the neck or shoulder and upper extremities in the 12 months before the study were associated with sickness absence for these complaints during the follow up. Workers with absence due to pain from back, neck or shoulder, upper extremities, or lower extremities were at higher risk of subsequent sickness absence in the next year