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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

MECHANISMS AND POTENTIAL THERAPY ON DISRUPTED BLOOD PRESSURE CIRCADIAN RHYTHM IN DIABETES

Hou, Tianfei 01 January 2018 (has links)
Arterial blood pressure (BP) undergoes a 24-hour oscillation that peaks in the active day and reaches a nadir at night during sleep in humans. Reduced nocturnal BP fall (also known as non-dipper) is the most common disruption of BP circadian rhythm and is associated with increased risk of untoward cardiovascular events and target organ injury. Up to 75% of diabetic patients are non-dippers. However, the mechanisms underlying diabetes associated non-dipping BP are largely unknown. To address this important question, we generated a novel diabetic db/db-mPer2Luc mouse model (db/db-mPer2Luc) that allows quantitatively measuring of mPER2 protein oscillation by real-time mPer2Luc bioluminescence monitoring in vitro and in vivo. Using this model, we demonstrated that the db/db-mPer2Luc mice have a diminished BP daily rhythm. The phase of the mPER2 daily oscillation is advanced to different extents in explanted peripheral tissues from the db/db-mPer2Luc mice relative to that in the control mice. However, no phase shift is found in the central oscillator, the suprachiasmatic nucleus (SCN). The results indicate that the desynchrony of mPER2 daily oscillation in the peripheral tissues contributes to the loss of BP daily oscillation in diabetes. Extensive research over the past decades has been focused on how the components of food (what we eat) and the amount of food (how much we eat) affect metabolic diseases. Only recently has it become appreciated that the timing of food intake (when we eat), independent of total caloric and macronutrient quality, is also critical for metabolic health. To investigate the potential effect of the timing of food intake on the BP circadian rhythm, we simultaneously monitored the BP and food intake profiles in the diabetic db/db and control mice using radiotelemetry and BioDAQ systems. We found the loss of BP daily rhythm is associated with disrupted food intake rhythm in the db/db mice. In addition, the normal BP daily rhythm is altered in the healthy mice with abnormal feeding pattern, in which the food is available only during the inactive-phase. To explore whether imposing a normal food intake pattern is able to prevent and restore the disruption of BP circadian rhythm, we conducted active-time restricted feeding (ATRF) in the db/db mice. Strikingly, ATRF completely prevents and restorers the disrupted BP daily rhythm in the db/db mice. While multiple mechanisms likely contribute to the protection of ATRF on the BP daily rhythm, we found that ATRF improves the rhythms of energy metabolism, sleep-wake cycle, BP-regulatory hormones and autonomic nervous system (ANS) in the db/db mice. To further investigate the molecular mechanism by which ATRF regulates BP circadian rhythm, we determined the effect of ATRF on the mRNA expressions of core clock genes and clock target genes in the db/db mice. Of particular interest is that we found among all the genes we examined, the mRNA oscillation of Bmal1, a key core clock gene, is disrupted by diabetes and selectively restored by the ATRF in multiple peripheral tissues in the db/db mice. More importantly, we demonstrated that Bmal1 is partially required for ATRF to protect the BP circadian rhythm. In summary, our findings indicate that the desynchrony of peripheral clocks contributes to the abnormal BP circadian pattern in diabetes. Moreover, our studies suggest ATRF as a novel and effective chronotherapy against the disruption of BP circadian rhythm in diabetes.
92

Measured Soil Hydraulic Properties as RZWQM2 Input to Simulate Soil Water Dynamics and Crop Evapotranspiration

Shahadha, Saadi Sattar 01 January 2018 (has links)
Agricultural system models integrate many different processes that cannot all be measured in field experiments and help quantify soil water dynamics, crop evapotranspiration, and crop growth with high temporal resolution. Understanding soil water dynamics and crop evapotranspiration is essential to improve agricultural management of field crops. For example, the interaction between nitrogen application rate and water dynamics is not sufficiently understood. In most cases, model simulations deviate from field measurements, especially when model input parameters are indirectly and unspecifically derived. The extent to which measured soil hydraulic property inputs decrease the discrepancy between measured and simulated soil water status is not well understood. Consequently, this study: (i) investigated thr use of measured soil hydraulic properties as Root Zone Water Quality Model (RZWQM2) inputs compared to indirectly derived inputs; (ii) explored the capability of calibrating measured soil hydraulic property input parameters for one crop and using them for other crops without further calibration; (iii) studied the effect of the nitrogen application rate on the behavior of soil water dynamics and crop evapotranspiration using RZWQM2 under different rainfall amounts. To evaluate the model in different field management conditions, a field experiment with soybean, corn, wheat, and fallow soil was conducted from 2015 – 2017 to collect field data to calibrate and validate the RZWQM2 model. The model presented a satisfactory response to using measured soil hydraulic property inputs and a satisfactory capability to quantify the effect of nitrogen rates on daily crop evapotranspiration, soil water dynamics, and crop growth. With sufficient measurements of soil hydraulic parameters, it was possible to build a RZWQM2 model that produced reasonable results even without calibration.
93

EVOLUTION OF EQUINE ARTERITIS VIRUS DURING PERSISTENT INFECTION IN THE REPRODUCTIVE TRACT OF THE STALLION AND THE MALE DONKEY

Nam, Bora 01 January 2017 (has links)
Equine arteritis virus (EAV) establishes persistent infection in the stallion reproductive tract, and the carrier stallion continues to shed virus in semen for weeks to years or lifelong. The objective of this study was to elucidate the intra-host evolution of EAV during persistent infection in stallions. Seven EAV seronegative stallions were experimentally infected with EAV KY84 strain and followed for 726 days post-infection, and sequential clinical samples including semen were collected for virus isolation and next-generation sequencing (NGS). In addition, archived sequential semen samples from two stallions that were naturally infected with EAV KY84 for a long-period (up to 10 years) were also sequenced by NGS. The data demonstrated genetic bottleneck event and selection during acute infection followed by intra-host quasispecies diversification during persistent infection in the stallion reproductive tract. Also, the full-length genome of a novel EAV donkey strain from Chile and a noncytopathic bovine viral diarrhea virus-1 (ncpBVDV-1) strain contaminating rabbit kidney-13 cells were also sequenced by NGS. The EAV donkey strain was genetically distinct but antigenically cross-reacted with EAV antisera, and it was phylogenetically closely related to the South African donkey strain of EAV. Genetic and phylogenetic analyses demonstrated that ncpBVDV-1 belongs to BVDV-1b group.
94

Characterization of the Marine Sponge Amphimedon compressa Microbiome Across a Spatial Gradient

Potens, Renee Michelle 20 May 2016 (has links)
Diverse and ecologically important microbial communities (microbiomes) are symbiotic within marine sponges. In this study, the microbiome of Amphimedon compressa from three sample locations (Broward and Dade Counties, Southeast Florida, USA and the Southern Caribbean, Bocas del Toro, Panama) is characterized using 16S rRNA Illumina sequencing. The predominant taxa are Proteobacteria and Cyanobacteria, as expected for Low Microbial Abundance sponges, accounting for over 53% of the total microbiome community. The numbers of Operational Taxonomic Units (OTUs) decrease from Broward County (2,900) to Dade County (2,300) and then Bocas del Toro (1,200). The correlates to a decreasing north-south gradient of sponge microbiome richness and diversity. Sponge microbiome richness and Alpha diversity are nearly identical from the two closest locations (37 km), both in Southeast Florida (Tukey HSD/ANOVA; p=0.999). However Panama sponge microbiome richness and Alpha diversity are distinctly lower, with the primary driver being distance, ~1,850 km from Southeast Florida. Abiotic factors driving this trend of decreased richness and diversity include increased temperature, and deceased salinity in relation to precipitation-based seasons. Sponge microbiome Beta diversity as determined by Bray-Curtis Dissimilarity and Non-Metric Multidimensional Scaling documents the clustering of Panama samples as distinct from the Broward and Dade County samples. In a seasonal comparison, Broward County sponge microbiome richness (p=0.026, r2=0.92) and Alpha diversity (p=0.007, r2=0.98) are significantly different, documenting robust effects of temperature. This comparison confirms lowest microbiome OTU diversity in the season with highest precipitation and highest temperatures of 29.8 °C. These results are consistent with prior studies that report decreasing microbiome OTU richness and diversity under conditions of environmental stress such as decreased salinity and increased temperatures.
95

RNAi Mediated Silencing of Cell Wall Invertase Inhibitors to Increase Sucrose Allocation to Sink Tissues in Transgenic Camelina Sativa Engineered with a Carbon Concentrating Mechanism

Zuber, Joshua 17 July 2015 (has links)
Plant invertases are a class of proteins that have enzymatic function in cleaving sucrose to fructose and glucose. Cell wall invertase, located on the exterior of the cell wall of plant cells, plays a key role in the unloading of sucrose from the apoplast to the sink tissues. Cell wall invertase interacts with an inhibitor, cell wall invertase inhibitor, post-transcriptionally to regulate its activity. The inhibitor is constitutively expressed in pollen development, early developing seeds, and senescing leaves: indicative of sucrose allocation being a limiting factor at these stages of development. We introduced algal bicarbonate transporters LCIA/CCP1 to Camelina sativa for the purpose of increasing photosynthetic capacity. The bicarbonate transporters concentrate CO2 at RuBisCO by pumping CO2 in the form of bicarbonate through the membrane, then converting it back to CO2 at RuBisCO, increasing CO2 concentration. Results from these plants have shown an increase in seed number, but not seed mass, along with a faster rate of maturity and senescence. This is indicative of acclimation to high CO2 conditions, resulting from insertion of the bicarbonate transporters. RNA sequencing was performed and a putative invertase inhibitor was recognized as being expressed in the transgenic C. sativa but not in the wild type. Our strategy is to knock out two invertase inhibitors using induced RNA silencing, dramatically altering sucrose allocation into developing seeds and resulting in an increase in seed biomass. It is the aim of this research to increase the biomass of C. sativa seeds in order to increase its effectiveness as an agent to create sustainable biofuels.
96

The impact of activity-based method on the performance of Science learners from selected junior secondary schools in Nigeria

Agbenyeku, Elizabeth Umoh 15 July 2017 (has links)
The study investigated the Impact of Activity-Based Teaching Method (ABTM) on students’ academic performance in basic science at Junior Secondary Schools in Katsina Metropolis, Nigeria. Three research questions and three research hypotheses were formulated to guide the researcher in the conduct of the research. The study randomly sampled three hundred and thirty (330) out of nine thousand and six (9,006) Junior III Basic Science Students. Three of the randomly selected schools were placed as experimental control groups. A total of one hundred and sixty five (165) students were randomly sorted out, each way, to constitute the experimental and control groups. A quasi-experimental pre-test-post-test research design was used for the study. A pre-test was administered to ascertain the equivalence of the two groups. The study subjects in the experimental group were taught a number of concepts enshrined in environmental management for sustainability using the assets in activity-based teaching method; the control group was taught the same content using the lecture method for eight weeks. The students were subjected to “Basic Science Achievement Test” (BSAT); this instrument provided data for addressing the research questions and hypotheses raised in the study; the hypotheses were tested using SPSS version 20.0 packaged at 0.05 level of significance; t-test for independent samples was used to test the hypotheses. The study revealed that basic science students taught using activity-based teaching strategy performed significantly higher than their counterparts who were only taught using lecture method; similarly, there was significant difference in the academic performance of males, as compared to female students; similarly the students exposed to activity-based teaching strategy demonstrated a higher retention ability indices in the learning of basic science concepts, as compared to their colleagues who were exposed only to the lecture method. The study recommended that teachers should employ activity-based teaching methodology (ABTM) in teaching concepts in basic science at Junior Secondary Schools in order to enhance academic performance and retention of the content that was taught. The study further recommended that there should be provisions in schools of facilities, provisions and equipment which are vital for effective implementation of activity-based teaching method (ABTM). / Curriculum and Instructional Studies / D. Ed. (Didactics)
97

Innate Immunity As Mediator of Cell Death and Inflammation in Alcoholic Liver Disease

Iracheta-Vellve, Arvin 01 November 2017 (has links)
Central driving forces in the pathogenesis of liver disease are hepatocyte death and immune cell-driven inflammation. The interplay between outcomes, stemming from these two major cell types, is present from the earliest ethanol exposure, and are both determinants in advanced stages of liver disease particularly in alcoholic liver disease (ALD). The complexities associated with advanced ALD are many and therapies are limited. Due to the liver’s role in ethanol metabolism and filtering gut-derived products, it is becoming increasingly clear that innate immunity plays a central role in triggering activation of cell death and inflammatory pathways in ALD. We identified interferon regulatory factor 3 (IRF3) activation as a mediator of hepatocyte death as the first event after ethanol exposure, and the inflammasome as a protein complex responsible for the subsequent inflammatory cascade, driven by the NLRP3 inflammasome. Our novel findings in murine samples and human patients with alcoholic hepatitis demonstrate that ethanol-induced inflammasome activity results in Caspase-1-mediated pyroptosis and extracellular ASC aggregates in the liver and circulation. Pyroptosis can be abrogated by therapeutic inhibition of inflammasome components, NLRP3 or Caspase-1. Taken together, the event leading to mtDNA release into the cytoplasm is the inception of the pathogenesis of ALD, triggering hepatocyte death, culminating in a pro-inflammatory cascade driven by the NLRP3 inflammasome and pyroptotic release of ASC.
98

A New Laser Pointer Driven Optical Microheater for Precise Local Heat Shock

Placinta, Mike 01 January 2009 (has links) (PDF)
The zebrafish has emerged as an important genetic model system for the study of vertebrate development. However, while genetics is a powerful tool for the study of early gene functions, the approach is more limited when it comes to understanding later functions of genes that have essential roles in early embryogenesis. There is thus a need to manipulate gene expression at different times, and ideally only in some regions of the developing embryo. Methods for conditional gene regulation have been established in Drosophila, C.elegans and the mouse, utilizing conditional gene activation systems such as the Gal4-UAS system (fly) and the cre/lox recombination system (mouse). While these tools are also being developed in zebrafish, the accessibility of the zebrafish embryo makes other approaches both possible and desirable. We have taken advantage of a heat-shock inducible system that uses the hsp70 promoter that is activated by cellular stress, such as heat. Having established that this global heat shock method allows temporal control of gene expression, we aimed to spatially control gene expression by applying controlled thermal heat to only a small region of the embryo. This would allow us to determine cell- and tissue-autonomous roles for developmentally important genes in an embryo with otherwise normal gene function. We have now developed a device that uses a laser to heat a defined region of the embryo, and thus activate the hsp70 promoter only in restricted regions of the embryo. The output of a 75 mW red laser pointer was focused into the 50 µm diameter core of an optical fiber, whose cleaved and coated end was used to heat, and thus induce, gene expression in a defined area. We have established conditions that allow controlled heating and trans-gene activation in small regions of the embryo without inducing cell death. This new tool will allow us to study the cell-autonomous roles of embryonic signaling molecules in cell differentiation, proliferation, and survival in a variety of tissues and at different times.
99

Improvement value of forest resources by use of cottonseed protein meal as a bio-based wood adhesive for hardwood plywood products

Entsminger, Edward David 09 August 2022 (has links) (PDF)
Literature shows that production of cottonseed adhesives is feasible to develop an environmentally friendly and competitive bio-based wood adhesive. Defatted cottonseed and water-washed cottonseed meals were prepared from glandless cottonseed and were used in adhesive formulations to produce three-ply yellow poplar (Liriodendron tulipifera) plywood panels as the first objective. These two cottonseed meals were compared with the properties of plywood panels made with an adhesive formulated from a commercial soybean meal, as a control. Adhesive resins were prepared from each protein meal with sodium metabisulfite (Na2S2O5) and one of two polyamido-amine-epichlorohydrin (PAE) wet strength agents, and the plywood panels were produced by hot pressing for 7, 8.5 and 10 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from three protein meals had comparable shear strengths. The combinations of the two cottonseed preparations and the two wet strength agents produced panels with acceptable wet resistant properties, whereas the soybean meal only produced acceptable panels with one of the wet strength agents. Because the panels prepared from the two cottonseed meals had comparable properties, there appears to be no benefit to including a water-washing step to increase the meal’s protein level. The second objective of this research was to reduce the hot press time and develop cottonseed meals into adhesives to become comparable to commercial soybean-based adhesives. New cottonseed, water-washed cottonseed, and commercial in-house soybean meals were separately prepared with deionized water, sodium metabisulfite, and PAE to produce three-ply yellow poplar plywood panels. The panels were hot pressed for 4, 5, and 6 minutes at 135°C with a constant pressure of 1.241 MPa. Panels prepared from the three meals and commercial soybean plywood panels had comparable mechanical shear strengths and water resistance properties. Results indicated that press time, meal types, and interactions were statistically significant. Shear strength results indicate that cottonseed could be used alternatively to soybean. The new cottonseed panels were more resistant to delamination than soybean. The cottonseed meals showed great promise for applicability as a formaldehyde-free, bio-based, and environmentally friendly hardwood plywood wood-based adhesives product for use in interior type applications.
100

Arrested and Aberrant: Effects of Amoxicillin in a Murine Model of Chlamydial Infection

Campbell, Regenia Beth Phillips 01 December 2013 (has links) (PDF)
Chlamydia trachomatis is the most common sexually transmitted bacterial disease agent worldwide, and, though frequently asymptomatic, can cause extreme pathology including infertility. Chlamydial species exhibit a unique biphasic developmental cycle. Once attached to a cell surface, infectious elementary bodies (EB) are internalized within an inclusion, the membrane-bound structure in which EB transform to noninfectious, replicable reticulate bodies (RB). After multiple rounds of division, RB condense to form EB, which are released and can infect new host cells. In culture, exposure to stressors, such as beta-lactam antibiotics, induce chlamydiae to reversibly detour from normal development into a noninfectious, viable state termed persistence. Cell culture data suggest that persistent forms are resistant to azithromycin (AZM), a front-line antibiotic, and are able to alter the host transcriptome. Though persistence has been described in culture for over 50 years, whether or not it: i) occurs in vivo; and ii) influences chlamydial pathogenesis, transmission and therapy has remained unresolved. To address these questions, we developed an animal model of persistent chlamydial infection using amoxicillin (AMX) treatment. AMX exposure decreased shedding of infectious chlamydiae in C. muridarum-infected mice without affecting chlamydial viability, demonstrating the presence of persistent chlamydiae. Shedding of infectious EB resumed following AMX cessation. Shedding data and microarray analyses suggested that host immunity might limit chlamydia’s exit from persistence in our model. Thus, we hypothesized that cyclophosphamide (CTX) treatment would increase the magnitude of chlamydial shedding observed after AMX-treatment cessation. CTX treatment increased post-AMX shedding by more than 10-fold compared to AMX-only controls. To determine whether persistent chlamydiae are resistant to antibiotic eradication in vivo, we induced persistence by administering AMX and treated mice with various AZM dosing regimes. Persistently infected mice demonstrated increased treatment failure following AZM therapy compared to productively infected controls. These data suggest that persistent chlamydiae are refractory to treatment in vivo and provide an explanation for the observation that treatment fails in some patients. In addition to creating the first fully characterized, experimentally tractable, in vivo model of chlamydial persistence, these experiments provide evidence that persistent/stressed chlamydial forms may serve as a long-term reservoir of infectious organisms in vivo.

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