Genetically engineered biofuel crops, such as switchgrass (Panicum virgatum L.), that produce their own cell wall-digesting cellulase enzymes would reduce costs of cellulosic biofuel production. To ...date, non-bioenergy plant models have been used in nearly all studies assessing the synthesis and activity of plant-produced fungal and bacterial cellulases. One potential source for cellulolytic enzyme genes is herbivorous insects adapted to digest plant cell walls. Here we examine the potential of transgenic switchgrass-produced TcEG1 cellulase from Tribolium castaneum (red flour beetle). This enzyme, when overproduced in Escherichia coli and Saccharomyces cerevisiae, efficiently digests cellulose at optima of 50 °C and pH 12.0. TcEG1 that was produced in green transgenic switchgrass tissue had a range of endoglucanase activity of 0.16–0.05 units (µM glucose release/min/mg) at 50 °C and pH 12.0. TcEG1 activity from air-dried leaves was unchanged from that from green tissue, but when tissue was dried in a desiccant oven (46 °C), specific enzyme activity decreased by 60%. When transgenic biomass was “dropped-in” into an alkaline buffer (pH 12.0) and allowed to incubate at 50 °C, cellobiose release was increased up to 77% over non-transgenic biomass. Saccharification was increased in one transgenic event by 28%, which had a concurrent decrease in lignin content of 9%. Histological analysis revealed an increase in cell wall thickness with no change to cell area or perimeter. Transgenic plants produced more, albeit narrower, tillers with equivalent dry biomass as the control. This work describes the first study in which an insect cellulase has been produced in transgenic plants; in this case, the dedicated bioenergy crop switchgrass. Switchgrass overexpressing the TcEG1 gene appeared to be morphologically similar to its non-transgenic control and produced equivalent dry biomass. Therefore, we propose TcEG1 transgenics could be bred with other transgenic germplasm (e.g., low-lignin lines) to yield new switchgrass with synergistically reduced recalcitrance to biofuel production. In addition, transgenes for other cell wall degrading enzymes may be stacked with TcEG1 in switchgrass to yield complementary cell wall digestion features and complete auto-hydrolysis.
Palms support the largest leaves in the world and have evolved on Earth for over 120 million years. They are often reported to be the only structure left standing post-hurricane. Cross-sectional ...shapes of cantilevered structures are important design factors affecting torsional and bending performance. Understanding the shape contribution of natural sections such as palm petioles (modified leaf stalks) is more difficult than those for simple 2D shapes because conventional methods of calculating section properties are not well suited to these irregular shapes. The role of internal structure, material properties and external shape of palm petioles in cantilever performance has been investigated and three main contributions to knowledge result from this research. Firstly, 3D mapping, i.e., the size, orientation and position, of vascular bundles in the Trachycarpus fortunei palm petiole reveals the distributions of stress and Young’s modulus values, providing a more detailed understanding of petioles than previous work. Secondly, bulk elastic material properties along the longitudinal axis of the same petiole are then input to a bi-layered model of the same petiole establishing the Young’s modulus of the two layers without mechanically testing them individually and for determining that the outer layer is not lignified. Thirdly, the largest contribution is the introduction of modified shape transformers employing the use of circular envelopes, eliminating error caused by approximating second moment of area with the torsional constant. This leads to a novel Shape Edge Mapping (SEM) technique which deconstructs petiole cross section shape elements and enables the structural contribution of these elements to be calculated, improving the understanding of the petiole section and how it relates to its mechanical function. This thesis makes a valuable addition to the knowledge of palm function and presents novel techniques for non-destructive extraction of natural shape data for abstraction and use in preliminary engineering design.
Nucleosomes are comprised of the histones H2A, H2B, H3 and H4, and serve as the core particles around which eukaryotic genomes are packaged into chromatin. The nucleosomes have been demonstrated to ...act as transcriptional repressors both in vitro and in vivo. In addition, the histones themselves have been shown to be functionally important for the proper regulation of gene expression. For example, it has previously been shown that the histone H3 and H4 N-termini are required to maintain proper repression of heterochromatic regions in the yeast, Saccharomyces cerevisiae. Further, regulation of the gene, GAL1, requires intact histone H3 and H4 N-termini. GAL1 is a galactose-responsive locus which is tightly regulated. The gene is switched on in galactose and off in glucose. However, if the N-termini are deleted from either histone H3 or H4, this precise regulation is disrupted. Histone H4 N-terminal deletions decrease the activation of GAL1 while histone H3 N-terminal deletions result in hyperactivation of the locus. This dissertation describes in detail how these histone mutations disrupt chromatin structure and how this may relate to the observed transcriptional phenotypes. In short, the deletion of the histone H4 N-terminus results in blockage of the GAL1 promoter and most likely prevents access of the activation machinery to the promoter. Histone H3 N-terminal deletions do not cause these same changes. Further, this thesis also details experiments which test whether these N-termini can substitute functionally for each other in either the capacity of GAL1 regulation or for silencing of the heterochromatic regions in yeast. It appears that the N-termini can be assigned context specific functions and that they cannot substitute for one another in any capacity other than maintenance of cellular viability. Finally, the last area of research discussed herein is a collection of data examining possibilities for mechanisms by which the histone N-termini may function in GAL1 regulation.
ABSTRACT
The computer‐based Praxis I: Academic Skills Assessment component of The Praxis Series: Professional Assessments for Beginning Teachers™ will include a measure of prospective teachers' ...writing proficiency. Current plans call for making available to test takers (before they take the exam) a pool of approximately 80 essay topics, from which the actual test topics will be drawn initially.
The objectives of the study described here were to predict the impact of this policy on the ways in which test takers will prepare for the test and to estimate the effect of this new practice on examinees' eventual test performance. To make these determinations, a small‐scale study was undertaken in collaboration with writing instructors at four different colleges or universities. Within the context of undergraduate writing courses at these institutions, instructors designed and conducted brief “coaching” programs in response to a challenge to provide any advice, instruction, tricks, etc., that might help their students achieve a minimally acceptable score on the test. A pool of 10 topics was disclosed and used in the coaching. Upon completion of the coaching, all students wrote two essays—one on a disclosed topic and one on a comparable, previously unseen topic.
Comparisons revealed very little difference between students' subsequent performances on these two types of topics. Performances on the two topics did not correlate differentially with any of three available indicators of academic ability/achievement. However, students believed that their writing skills were better revealed by writing on disclosed topics than on topics that had not been previously seen. In short, the study uncovered little to suggest that plans for disclosing a pool of Praxis I essay topics should be modified.
The nuclear receptors LXRα and LXRβ have been implicated in the control of cholesterol and fatty acid metabolism in multiple cell types. Activation of these receptors stimulates cholesterol efflux in ...macrophages, promotes bile acid synthesis in liver, and inhibits intestinal cholesterol absorption, actions that would collectively be expected to reduce atherosclerotic risk. However, synthetic LXR ligands have also been shown to induce lipogenesis and hypertriglyceridemia in mice, raising questions as to the net effects of these compounds on the development of cardiovascular disease. We demonstrate here that the nonsteroidal LXR agonist GW3965 has potent antiatherogenic activity in two different murine models. In LDLR-/-mice, GW3965 reduced lesion area by 53% in males and 34% in females. A similar reduction of 47% was observed in male apoE-/-mice. Long-term (12-week) treatment with LXR agonist had differential effects on plasma lipid profiles in LDLR-/-and apoE-/-mice. GW3965 induced expression of ATP-binding cassettes A1 and G1 in modified low-density lipoprotein-loaded macrophages in vitro as well as in the aortas of hyperlipidemic mice, suggesting that direct actions of LXR ligands on vascular gene expression are likely to contribute to their antiatherogenic effects. These observations provide direct evidence for an atheroprotective effect of LXR agonists and support their further evaluation as potential modulators of human cardiovascular disease.
Health disparities research in the United States over the past 2 decades has yielded considerable progress and contributed to a developing evidence base for interventions that tackle disparities in ...health status and access to care. However, health disparity interventions have focused primarily on individual and interpersonal factors, which are often limited in their ability to yield sustained improvements. Health disparities emerge and persist through complex mechanisms that include socioeconomic, environmental, and system-level factors. To accelerate the reduction of health disparities and yield enduring health outcomes requires broader approaches that intervene upon these structural determinants. Although an increasing number of innovative programs and policies have been deployed to address structural determinants, few explicitly focused on their impact on minority health and health disparities. Rigorously evaluated, evidence-based structural interventions are needed to address multilevel structural determinants that systemically lead to and perpetuate social and health inequities. This article highlights examples of structural interventions that have yielded health benefits, discusses challenges and opportunities for accelerating improvements in minority health, and proposes recommendations to foster the development of structural interventions likely to advance health disparities research.
A series of improvements to the standard solid phase peptide synthesis (SPPS) process allowing for significant gains in product purity along with only a 4 min standard cycle time and a 90% reduction ...in total waste produced is reported. For example, syntheses of the well-known 65–74acyl carrier protein (ACP) and 1–42β-amyloid peptides were accomplished with 93 and 72% purity (UPLC–MS) in only 44 and 229 min, respectively.
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