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  Partner: UNT Libraries
 Language: English
 Collection: UNT Theses and Dissertations
Metabolic, cardiac and ventilatory regulation in early larvae of the South African clawed frog, Xenopus laevis.

Metabolic, cardiac and ventilatory regulation in early larvae of the South African clawed frog, Xenopus laevis.

Date: December 2009
Creator: Pan, Tien-Chien
Description: Early development of O2 chemoreception and hypoxic responses under normoxic (150 mmHg) and chronically hypoxic (110 mmHg) conditions were investigated in Xenopus laevis from hatching to 3 weeks post fertilization. Development, growth, O2 consumption, ventilatory and cardiac performance, and branchial neuroepithelial cells (NEC) density and size were determined. At 3 days post fertilization (dpf), larvae started gill ventilation at a rate of 28 ± 4 beats/min and showed increased frequency to 60 ± 2 beats/min at a PO2 of 30 mmHg. Also at 3 dpf, NECs were identified in the gill filament buds using immunohistochemical methods. Lung ventilation began at 5 dpf and exhibited a 3-fold increase in frequency from normoxia to a PO2 of 30 mmHg. Hypoxic tachycardia developed at 5 dpf, causing an increase of 20 beats/min in heart rate, which led to a 2-fold increase in mass-specific cardiac output at a PO2 of 70 mmHg. At 10 dpf, gill ventilatory sensitivity to hypoxia increased, which was associated with the increase in NEC density, from 15 ± 1 to 29 ± 2 cells/mm of filament at 5 and 10 dpf, respectively. Unlike the elevated rate, cardiac and ventilatory volumes were independent of acute hypoxia. Despite increased cardioventilatory frequency, ...
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Metabolic Engineering in Plants to Control Source/sink Relationship and Biomass Distribution

Metabolic Engineering in Plants to Control Source/sink Relationship and Biomass Distribution

Date: August 2013
Creator: Lahiri, Ipsita
Description: Traditional methods like pruning and breeding have historically been used in crop production to divert photoassimilates to harvested organs, but molecular biotechnology is now poised to significantly increase yield by manipulating resource partitioning. It was hypothesized that metabolic engineering in targeted sink tissues can favor resource partitioning to increase harvest. Raffinose Family Oligosaccharides (RFOs) are naturally occurring oligosaccharides that are widespread in plants and are responsible for carbon transport, storage and protection against cold and drought stress. Transgenic plants (GRS47, GRS63) were engineered to generate and transport more RFOs through the phloem than the wild type plants. The transgenic lines produced more RFOs and the RFOs were also detected in their phloem exudates. But the 14CO2 labeling and subsequent thin layer chromatography analysis showed that the RFOs were most likely sequestered in an inactive pool and accumulate over time. Crossing GRS47 and GRS63 lines with MIPS1 plants (that produces more myo-inositol, a substrate in the RFO biosynthetic pathway) did not significantly increase the RFOs in the crossed lines. For future manipulation of RFO degradation in sink organs, the roles of the endogenous α-galactosidases were analyzed. The alkaline α-galactosidases (AtSIP1 and AtSIP2 in Arabidopsis) are most likely responsible for digesting RFOs ...
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Metabolic Engineering of Raffinose-Family Oligosaccharides in the Phloem Reveals Alterations in Patterns of Carbon Partitioning and Enhances Resistance to Green Peach Aphid

Metabolic Engineering of Raffinose-Family Oligosaccharides in the Phloem Reveals Alterations in Patterns of Carbon Partitioning and Enhances Resistance to Green Peach Aphid

Date: August 2010
Creator: Cao, Te
Description: Phloem transport is along hydrostatic pressure gradients generated by differences in solute concentration between source and sink tissues. Numerous species accumulate raffinose-family oligosaccharides (RFOs) in the phloem of mature leaves to accentuate the pressure gradient between source and sinks. In this study, metabolic engineering was used to generate RFOs at the inception of the translocation stream of Arabidopsis thaliana, which transports predominantly sucrose. To do this, three genes, GALACTINOL SYNTHASE, RAFFINOSE SYNTHASE and STACHYOSE SYNTHASE, were expressed from promoters specific to the companion cells of minor veins. Two transgenic lines homozygous for all three genes (GRS63 and GRS47) were selected for further analysis. Sugars were extracted and quantified by high performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD), and 21-day old plants of both lines had levels of galactinol, raffinose, and stachyose approaching 50% of total soluble sugar. All three exotic sugars were also identified in phloem exudates from excised leaves of transgenic plants whereas levels were negligible in exudates from wild type leaves. Differences in starch accumulation or degradation between wild type and GRS63 and GRS47 lines were not observed. Similarly, there were no differences in vegetative growth between wild type and engineered plants, but engineered plants flowered ...
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Metabolic Syndrome and Psychosocial Factors

Metabolic Syndrome and Psychosocial Factors

Date: August 2009
Creator: Tweedy, Maureen P.
Description: Metabolic syndrome is a constellation of risk factors, including abdominal obesity, hypertriglyceridemia, low HDL cholesterol, high blood pressure, and high fasting glucose, that commonly cluster together and can result in cardiovascular disease. The prevalence of metabolic syndrome and the components that comprise the syndrome vary by age and by racial/ethnic group. In addition, previous research has indicated that the risk factors contributing to metabolic syndrome may be exacerbated by exposure to perceived stress. This study utilized data from the 2002, 2004, and 2006 Health and Retirement Study (HRS) and National Health and Nutrition Examination Survey (NHANES) data sets. It was hypothesized that depression and anxiety (conceptualized as stress in this study) increase the risk of presenting with metabolic syndrome while social support decreases the risk of metabolic syndrome. While results of cross-sectional analysis do not indicate a significant relationship between depression and metabolic syndrome (t = -.84, ns), longitudinal analysis does indicate a significant relationship between depression and metabolic syndrome over time (t = -5.20, p <.001). However, anxiety is not significantly related to metabolic syndrome when the relationship is examined through cross-sectional analysis (t = -1.51, ns) and longitudinal analysis (&#967;² = 13.83, ns). Similarly, social support is not ...
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Metabolism of Hydrocortisone by X-Irradiated Rat Liver Tissue as Determined by the Porter-Silber Chromagen Method

Metabolism of Hydrocortisone by X-Irradiated Rat Liver Tissue as Determined by the Porter-Silber Chromagen Method

Date: August 1959
Creator: Pryor, Nan Webb
Description: The present study may be considered endocrinological and radiobiological in nature. The endocrinology phase was concerned with studying the changes in endocrine function following the application of a stress agent. X-irradiation was chosen as the stressor in order to determine any difference in effect of this stressor from others which have been studied, e. g. heat, cold, metabolic poisons. Liver slices taken from rats at various time intervals following whole body X-irradiation were tested for their ability to metabolize hydrocortisone from a Krebs-Ringer solution.
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Metabolism of Methylglyoxal by Scenedesmus Quadricauda

Metabolism of Methylglyoxal by Scenedesmus Quadricauda

Date: June 1970
Creator: Rounsavall, Terry Yale
Description: The purpose of this study was to investigate the metabolic pathways of methylglyoxal in S. quadricauda.
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Metacognition, Motivation, and Learning: A Study of Sixth-Grade Middle School Students' Use and Development of Self-Regulated Learning Strategies

Metacognition, Motivation, and Learning: A Study of Sixth-Grade Middle School Students' Use and Development of Self-Regulated Learning Strategies

Date: December 1993
Creator: Shapley, Kelly S.
Description: This study investigated whether students can be taught to use self-regulated strategies.
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Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field

Metal-Aluminum Oxide Interactions: Effects of Surface Hydroxylation and High Electric Field

Date: December 2001
Creator: Niu, Chengyu
Description: Metal and oxide interactions are of broad scientific and technological interest in areas such as heterogeneous catalysis, microelectronics, composite materials, and corrosion. In the real world, such interactions are often complicated by the presence of interfacial impurities and/or high electric fields that may change the thermodynamic and kinetic behaviors of the metal/oxide interfaces. This research includes: (1) the surface hydroxylation effects on the aluminum oxide interactions with copper adlayers, and (2) effects of high electric fields on the interface of thin aluminum oxide films and Ni3Al substrate. X-ray photoelectron spectroscopy (XPS) studies and first principles calculations have been carried out to compare copper adsorption on heavily hydroxylated a- Al2O3(0001) with dehydroxylated surfaces produced by Argon ion sputtering followed by annealing in oxygen. For a heavily hydroxylated surface with OH coverage of 0.47 monolayer (ML), sputter deposition of copper at 300 K results in a maximum Cu(I) coverage of ~0.35 ML, in agreement with theoretical predictions. Maximum Cu(I) coverage at 300 K decreases with decreasing surface hydroxylation. Exposure of a partially dehydroxylated a-Al2O3(0001) surface to either air or 2 Torr water vapor results in recovery of surface hydroxylation, which in turn increases the maximum Cu(I) coverage. The ability of surface hydroxyl ...
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Metal Complexes of 2,3-Quinoxalinedithiol

Metal Complexes of 2,3-Quinoxalinedithiol

Date: May 1969
Creator: Ganguli, Kalyan Kumar, 1912-
Description: A series of new planar complexes with the dianion of 2,3-quinoxalinedithiol ligand has been prepared. The complexes have been characterized from the study of their analyses, magnetic moment, conductance, polarograms, electron spin resonance spectra, and electronic spectra, and compared with the available data on the corresponding maleonitriledithiolene and toluene-3,4-dithiolene complexes.
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Metal (II) Complexes with N-Salicylideneamino Acids

Metal (II) Complexes with N-Salicylideneamino Acids

Date: August 1969
Creator: Carlisle, Gene Ozelle
Description: Transition metal complexes derived from Schiff bases have rendered an important contribution to the development of modern coordination chemistry. Various stable compounds have been prepared having synthetic, biological, and physicochemical interest. In particular, complexes of salicylaldimines, B-ketoamines, and closely related ligand systems have been investigated.
Contributing Partner: UNT Libraries