2009 MU theses - Freely available online
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Item Progestin regulation of follicular dynamics in beef cattle(University of Missouri--Columbia, 2009) Risley, Mallory Elise, 1985-; Smith, Michael FieldingProgestins, such as melengestrol acetate (MGA) and Controlled Internal Drug Release (CIDR), can inhibit ovulation and synchronize estrus in cattle. However, long-term MGA treatment, in the absence of a corpus luteum, results in the formation of a persistent follicle (PF). Fertilization of a oocyte ovulated from a PF is associated with decreased pregnancy rates. The overall objectives were to determine the effect of 14 days of progestin (CIDR) treatment on follicular dynamics (length of follicular wave and maximum follicle diameter) and serum concentrations of progesterone (P4) in beef cattle treated with a new or previously used CIDR. Serum concentrations of P4 for heifers in the New and Used CIDR groups were similar (P [greater than] 0.1) throughout the 14 d treatment period but lower than in the Control group (normal luteal phase). Length of a follicular wave was longer (P [less than] 0.05) in the progestin-treated groups compared to the Control group. For heifers, dominant follicle diameter was greater (P [less than] 0.05) in the Used CIDR group compared to Control heifers; whereas, in cows maximum follicle diameter was similar in the New and Used CIDR groups and greater (P [less than] 0.05) than in the Control group. Serum estradiol concentrations were elevated (P [less than] 0.05) in the progestin treated groups compared to control animals on most days of the treatment period. In summary, long-term CIDR treatment, in the absence of a CL, induced the formation of a PF in both heifers and cows based on increased length of follicular wave, increased follicle diameter, and increased serum estradiol concentrations.Item Synthesis of rhenium complexes as models for new sigma receptor imaging agents(University of Missouri--Columbia, 2009) Chen, Peter, 1984-; Lever, Susan Z., 1952-The sigma receptor has been biologically found to play roles in the central nervous system (CNS) disorders and cancer cell proliferation. With the identification of lead sigma receptor binding ligands by previous structure activity relationship (SAR) studies, new sigma Tc-⁹⁹[superscript m] sigma receptor imaging agents were designed. Tc-⁹⁹ [superscript m] imaging agents provide the advantages for routing clinical use due to its ideal nuclear properties (t₁/₂=6 hours and 140 keV gamma photon emission) and being readily available from a ⁹⁹Mo/⁹⁹[superscript m] Tc generator. The stability, structure, and biodistribution of rhenium complexes have been found similar to their Tc-⁹⁹ [superscript m] counterparts. Non-radioactive rhenium surrogates serve as a useful precursor for the radioactive Tc-⁹⁹ [superscript m] imaging agents. The Re/Tc-⁹⁹ [superscript m] are bound by the amide-amine-dithiol tetradentate (AADT) chelate and linked onto the sigma moieties following the bifunctional chelate approach. The current study, successfully synthesized the chelate, sigma moieties, and target rhenium surrogates toward the goal of developing new sigma receptor imaging agents.Item Influence of herbicide applications and common pasture weeds on total forage yield and nutritive values in tall fescue pastures and hayfields in Missouri(University of Missouri--Columbia, 2009) Payne, Kristin K., 1984-; Bradley, Kevin W. (Kevin Wayne), 1973-The addition of several new herbicides labeled for pastures or hayfields has led many growers to question their options for weed management in these environments. In addition, little is known about the influence of common pasture weed species on total biomass yield and nutritive values in a pasture or hayfield setting. Therefore, research was conducted to 1) evaluate the effect of various herbicides on the control of tall goldenrod (Solidago canadensis subsp. altissima (L.)), common ragweed (Ambrosia artemisiifolia L.), and tall ironweed (Vernonia gigantea (Walt.) Trel), 2) evaluate the effect of herbicides on total biomass yield and nutritive values, and 3) evaluate the effects of increasing densities of common ragweed and common cocklebur (Xanthium strumarium L.) on total biomass yield and nutritive values. Results from these experiments indicate that a variety of herbicide treatments will provide good control of several common pasture weed species, but that infestations of these weeds may not necessarily reduce the nutritive values or yield of the total biomass harvested. For example, biomass yield increased from 1 to 6 kg ha⁻¹ and crude protein decreased by 0.4 g kg⁻¹ as common ragweed or common cocklebur density increase within a tall fescue stand. In all experiments, nutritive values of pure weed species samples revealed that most pasture weed species provide greater values than pure tall fescue when forage harvests occur in June. Additional research is necessary to investigate why these species are not consumed by cattle and continue to be a problem in Missouri tall fescue pastures and hayfields.Item Polarimetric radar processing of AIRSAR imagery from Los Angeles basin region(University of Missouri--Columbia, 2009) Hedrick, Andrew T., 1983-; Legarsky, Justin J.Extracting useful information and intelligence from polarimetric interferometric synthetic aperture radar (PolInSAR) data involves a variety of highly sophisticated processing methods. To aid in the advancement of efficient PolInSAR processing techniques, an investigation of underlying scattering mechanisms such as coherent scatterers (CS) and polarimetric decomposition techniques is conducted in this study using JPL AIRSAR fully polarimetric data over a portion of the greater Los Angeles area. For this study, selection of the overall optimum polarization showed an increase of CS candidates compared to standard polarizations. In addition, polarimetric decomposition ([alpha]-H and F/D) analysis of CS and non-CS (NCS) pixels found a trend of increasing double-bounce scattering, Fd, with decreasing volume scattering, Fv, and polarimetric Entropy, H, for CS relative to NCS.Item High throughput profiling of transcription factors involved in soybean root growth under water deficit(University of Missouri--Columbia, 2009) Tran, Huong Nguyen Thanh, 1983-; Nguyen, Henry T.Drought is the major abiotic stress factor limiting crop productivity worldwide. Plant root and shoot systems respond to environmental changes by altering the expression of complex gene networks through sensing environmental stresses and modifying signaling and metabolic pathways. Previous work (Yamaguchi et al., 2009) showed that the soybean primary root adapts to low water potential (-1.6 MPa) by maintaining longitudinal expansion in the apical 4 mm (region 1), whereas in the adjacent 4 mm (region 2), longitudinal expansion reaches a maximum in well-watered roots but is progressively inhibited at low water potential. To identify the key transcription factors (TFs) that determine these responses to low water potential, we have conducted high-throughput profiling of root-related TF expression in regions 1 and 2 of water-stressed and well-watered roots using quantitative real-time PCR. 186 root- and stress-related TFs were selected to identify their specific expression patterns in root regions 1 and 2 of well-watered and water-stressed soybean seedlings at four time points (5h, 12h, 24h, and 48h) after transplanting. Several stress-specific and root-region-specific transcripts were identified which may contribute to root responses to water deficits. Among these were zinc-finger protein, MYB-related protein, GmNAC3, GmNAC4, and bZIP transcription factors. These TFs were differentially expressed in distinct root regions, and therefore they can be targeted for functional characterization and further genetic engineering for enhanced drought resistance in soybean.