UNT Libraries - 14 Matching Results
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- Developmental Patterns of Metabolism and Hematology in the Late Stage Chicken Embryo (Gallus Domesticus) at Two Incubation Temperatures.
- How temperature affects physiological development in the chicken embryo is unknown. Embryos incubated at 38°C or 35°C showed no difference in growth or survival. The time to hatching was longer in 35°C than 38°C embryos (23.7 vs. 20.6 days), but unaffected was the relative timing of appearance of developmental landmarks (internal, external pipping). At stage 43-44, 38°C embryos maintained oxygen consumption around 1 mL/g/h despite acute temperature reduction (suggesting thermoregulatory maturation), unlike 35°C embryos. In 35°C embryos the lower oxygen-carrying capacity and temperature insensitive blood O2 affinity (P50 about 30 mmHg) may restrict O2 delivery to tissues, limiting metabolism during decreased ambient temperature. Reduced incubation temperature retards normal hematological and thermoregulatory development.
- Morphological and Hematological Responses to Hypoxia During Development in the Japanese quail, Coturnix coturnix
- Hypoxic responses in quail development differ depending upon stage, duration and level of oxygen partial pressure of embryo. Incubation was switched to/from 110mmHg partial pressure (hypoxia), to/from 150mmHg (normoxia) during different stages in development, and control was incubated in normoxia throughout. Hatchability and embryo survival resulted in no hatchlings in continuous hypoxia. Responses to various hypoxic exposures throughout development resulted in recovery/repair of hypoxic damage by hatch. Heart and body mass, beak and toe length, hemoglobin, and hematocrit were measured to determine embryo responses to hypoxia during development at days 10, 15, and hatch. Hypoxia seemed to have the most deleterious effects on eggs in continuous hypoxia. Collectively, data indicate critical developmental windows for hypoxia susceptibility, especially during mid-embryonic development.
- Use of Geographic Information System and Remote Sensing Technologies to Describe Mosquito Population Dynamics in the Ray Roberts Greenbelt, Denton County, Texas
- A population survey was conducted from April through September 2002 on mosquito species occurring on the Ray Roberts Greenbelt, a riparian corridor used for public recreation on the Elm Fork of the Trinity River, in Denton County, Texas. ArcGIS software was used to set up a stratified random sampling design based on habitat parameters. Multivariate analyses of sampling data and climatic variables were used to describe spatial and temporal patterns of mosquito species. A total of 33 species were collected during this study belonging to the following genera: Aedes, Anopheles, Coquillettidia, Culex, Mansonia, Ochlerotatus, Orthopodomyia, Psorophora, Toxorhynchites, and Uranotaenia. Seasonal distributions of the dominant species revealed population fluctuations. Aedes vexans was the primary species collected in April and May, occurring in low numbers throughout the rest of the sampling period. Psorophora columbiae reached its highest population density in June, with a smaller peak occurring in late July. Present from May through the end of September, Culex erraticus was the most abundant species collected with major peaks in mid-June and the end of July. Abundance of Culex salinarius followed the same general trend as that for Cx. erraticus, but with smaller numbers. The specimens were tested for a variety of arboviruses by the Texas Department of Health. One pool of Cx. erraticus and Cx. salinarius, collected in August 2002, tested positive for West Nile virus. Variables that were important factors for determining dominant species abundance were temperature, wind speed, rain accumulation occurring one-week and two-weeks prior to sampling, number of day since last rain event, dew point, and average canopy coverage.
- Analysis and expression of the cotton gene for the D-12 fatty acid desaturases 2-4 (FAD2-4)
- A genomic clone containing a 16.9-kb segment of cotton DNA was found to encompass a D-12 fatty acid desaturases (FAD2-4) gene. The FAD2-4 gene has a single, large intron of 2,780 bp in its 5'-untranslated region, just 12 bp upstream from the ATG initiation codon of the FAD2-4 opening reading frame. A number of prospective promoter elements, including several light-responsive sequences, occur in the 5'-flanking region. The coding region of the gene is 1155 bp with no introns, and would encode a FAD2-4 polypeptide of 384 amino acids. The putative protein had four membrane-spanning helices, hallmarks of an integral membrane protein, and would probably be located in the endoplasmic reticulum. The FAD2-4 gene is indeed a functional gene, since yeast cells transformed with a plasmid containing the coding region of the gene synthesize an appreciable amount of linoleic acid (18:2), not normally made in wild-type yeast cells. The FAD2-4 gene has many structural similarities to the cotton FAD2-3 gene that was also analyzed in this laboratory.
- Applications of Remote Sensing and GIS to Modeling Fire for Vegetative Restoration in Northern Arizona
- An accurate fire model is a useful tool in predicting the behavior of a prescribed fire. Simulation of fire requires an extensive amount of data and can be accomplished best using GIS applications. This paper demonstrates integrative procedures of using of ArcGIS™, ERDAS Imagine™, GPS, and FARSITE© to predict prescribed fire behavior on the Kaibab-Paiute Reservation. ArcGIS was used to create a database incorporating all variables into a common spatial reference system and format for the FARSITE model. ArcGIS Spatial Analyst was then used to select optimal burn sites for simulation. Our predictions will be implemented in future interagency efforts towards vegetative restoration on the reservation.
- Storm Water System Monitoring for the Small Municipality Under Phase II of the National Pollutant Discharge Elimination System
- Storm water quality can have a significant impact on receiving water bodies. The chief recipients of these impacts are aquatic life in the receiving water body and downstream water users. Over the last few decades, legislation, regulations, institutions and facilities have evolved to recognize the impact of urban storm water on receiving streams. This increased emphasis has caused contaminants in storm water to be identified as a major concern. This developing concern has generated an increased interest in the water quality of our streams and lakes and emphasized the need for more monitoring efforts. With the passage of the National Pollutant Discharge Elimination System (NPDES) Phase II requirements, small municipalities are responsible for storm water impacts on receiving waters within their jurisdiction. For the purposes of NPDES Phase II requirements, small municipalities are identified as these municipalities that are typically composed of 10,000 but less than 100,000 in population. The purpose of this dissertation is to develop a manual for use by the staff of small municipalities in meeting the requirements prescribed by changes initiated in the NPDES Phase II regulations. Attempts were made to comply with these requirements within a very limited manpower and budget framework and to develop procedures that would allow for permit compliance using testing equipment that was both reliable and robust. The users' manual provides valuable guidance in the establishment of a knowledge base for characterization of the watersheds selected for study. Chapter 3 of the dissertation contains a users' manual, designed for use by municipal staff members in their efforts to comply with the NPDES Phase II requirements. Using the techniques and equipment capabilities developed during the writing of the users' manual a characterization of three watersheds within Denton County, Texas was developed. Non-storm water samples were taken from each of the streams and …
- Analysis of a Cotton Gene Cluster for the Antifungal Protein Osmotin
- Three overlapping genomic clones covering 29.0 kilobases of cotton DNA were found to encompass a cluster of two presumptive osmotin genes (OSMI and OSMII) and two osmotin pseudogenes (OSMIII and OSMIV). A segment of 16,007 basepairs of genomic DNA was sequenced from the overlapping genomic clones (GenBank Accessions AY303690 and AF304007). The two cotton osmotin genes were found to have open reading frames of 729 basepairs without any introns, and would encode presumptive osmotin preproteins of 242 amino acids. The open reading frames of the genes are identical in sequence to two corresponding cDNA clones (GenBank Accessions AF192271 and AY301283). The two cDNA inserts are almost full-length, since one lacks codons for the four N-terminal amino acids, and the other cDNA insert lacks the coding region for the 34 N-terminal amino acids. The cotton osmotin preproteins can be identified as PR5 proteins from their similarities to the deduced amino acid sequences of other plant osmotin PR5 preproteins. The preproteins would have N-terminal signal sequences of 24 amino acids, and the mature 24 kilodalton isoforms would likely be targeted for extracellular secretion. Prospective promoter elements, including two ethylene response elements, implicated as being positive regulatory elements in the expression of a number of PR-proteins, occur in the 5'-flanking regions. The mature osmotin proteins accumulate in cotton plants treated with the inducers ethephon and hydrogen peroxide. Thus, the two cotton osmotin genes encode osmotin proteins. The coding regions of the two genes have been expressed and isolated as fusion polypeptides in a bacterial expression system. Binary constructs containing the open reading frames of the two osmotin genes under the control of the 35S CaMV promoter have been generated for eventual production of transgenic Arabidopsis and cotton plants for potential constitutive expression of the osmotin proteins for increased resistance against fungal pathogens.
- The aquatic insect communities of Holbrook Creek and Cochetopa Creek in Colorado.
- The first objective for this problem in lieu of thesis project was to gather, identify to the lowest practical taxonomic level and organize all available aquatic insects collected from high altitude Colorado aquatic systems during the summers of 1994, 1996, 1998, and 2002 for the University of North Texas Environmental Science Field Course (BIOL 5650). The curated collection will be housed in the Elm Fork Natural History Museum, located at the University of North Texas. The second objective was to provide a summary and discussion of the occurrence and distribution of the aquatic insects collected from Mt. Blanca in 1994, 1996, and 1998 and to create a taxa list of aquatic insects collected from Cochetopa Creek during the summer of 2002.
- Comparative Bioavailability of Dietary and Dissolved Cadmium to Freshwater Aquatic Snails
- Heavy metal bioaccumulation in aquatic organisms may occur through direct or indirect uptake routes. Research indicates that the significance of uptake route varies with contaminant and organism exposed. The relative importance of different metal sources in aquatic systems was investigated by exposing freshwater snails to dietary or dissolved sources of cadmium. Snails were exposed to control, contaminated food only, contaminated water only, and contaminated food and water treatments. During the 15-day exposure, samples were taken to determine Cd concentration in snail soft tissue, snail shell, algal food, and overlying water. Analyses of snail soft tissue and shells indicate that exposure route significantly affects Cd concentrations in the tissues. In both cases, dissolved Cd is the primary contributor to metal body burden.
- Influence of Cholesterol Import on Aspergillus fumigatus Growth and Antifungal Suscepibility
- Invasive pulmonary aspergillosis is a life-threatening fungal infection commonly observed in immunocompromised patients and has a mortality rate approaching 100% once the disease is disseminated. Aspergillus fumigatus is the most common pathogen. Early diagnosis improves the prognosis but is very difficult since most signs and symptoms are nonspecific. Antifungal therapy, usually based on sterol biosynthesis inhibitors, is also of limited efficacy. In my attempts to discover a diagnostic sterol marker for aspergillosis, I observed that A. fumigatus incorporates large amounts of cholesterol from serum-containing medium. This observation suggested the hypothesis that exogenous cholesterol from the host can be imported by A. fumigatus and used as a substitute for ergosterol in the cell membrane. This proposed mechanism would reduce the efficacy of antifungal drugs that act as sterol biosynthesis inhibitors. Experiments to test this hypothesis were designed to determine the effects of serum-free and serum-containing medium on growth of A. fumigatus in the presence and absence of azole antifungal agents. The results showed a marked increase in growth in the presence of human serum. Cultures in media containing cholesterol but no serum also showed enhanced growth, a result indicating that a non-cholesterol component of serum is not primarily responsible for the increased growth. However, sterol analysis of A. fumigatus cultured in the absence of inhibitors showed little or no change in ergosterol levels. This result suggested that the imported cholesterol was not being used as membrane sterol. However, in parallel experiments using Itraconazole, an antifungal agent that attenuates sterol biosynthesis by inhibiting the sterol 14a-demethylase (ERG11), ergosterol levels decreased with increasing doses of inhibitor. Moreover, serum-containing medium partially rescued A. fumigatus from the effects of Itraconazole, and a similar rescue effect was observed with serum-free media containing cholesterol. From the preceding results, it can be concluded that human serum enhances A. …
- Management Tools for Prescribed Burning for Tallgrass Prairie Restoration at the Lewisville Lake Environmental Learning Area
- The Lewisville Lake Environmental Learning Area (LLELA) is a wildlife management area with tallgrass prairie, an endangered ecosystem. Essential ecosystem processes, especially fire, are part of restoration. To support fire management efforts at LLELA and surrounding areas, this project evaluated and developed tools for fire restoration. The four primary prairie grasses respond favorably to burning. Fuel loads and fuel models vary by scale and survey method. One- and 10-hour fuel moisture can be predicted using a statistical model; 100- and 1,000-hour fuel moisture cannot. Historic weather data suggests that burning can occur when it is most effective. The production of ozone precursors produced by burning is comparable to those emitted every six minutes by regional automobiles.
- Modeling of Land Use Change Effects on Storm Water Quantity and Quality in the City of Carrollton and the North Texas Area
- Development and population are rapidly increasing in urbanizing areas of North Texas and so is the need to understand changes in storm water runoff flow and its contamination by nutrients, sediment, pesticides and other toxicants. This study contributes to this understanding and has two primary components: first, development of a graphical user interface for a geographic information system and storm water management database, and second, performing a two-scale hydrological modeling approach (the US Corp of Engineers HEC-HMS model and the US Environmental Protection Agency SWMM model). Both primary components are used together as a toolkit to support the storm water management program of the City of Carrollton, located in North Texas. By focusing limited city resources, the toolkit helps storm water managers in the process of compliance with federal regulations, especially the National Pollution Discharge Elimination System permit, and provides guidance for reporting, planning and investigation. A planning example was conducted by modeling potential changes in storm water quality due to projections of land use based on the City of Carrollton's Comprehensive Plan. An additional component of this study is the evaluation of future changes in surface water quantity and quality in the North Central Texas area, specifically in a rural but rapidly urbanizing subbasin area of the greater Lake Lewisville watershed. This was accomplished using the US Corp of Engineers HEC-HMS hydrological model. Precipitation scenarios were derived from years of historically high, medium, and low annual precipitation. Development scenarios were derived from current land use in the Lake Lewisville sub basin, current land use in the city of Carrollton, and from Markov projections based on recent land use change calculated from satellite images of 1988 and 1999. This information is useful for future land use planning and management of water resources in North Texas.
- Pyrimidine Genes in Pseudomonas Species
- This thesis is a comparative study of gene arrangements in Pseudomonas species, and is organized into three major sections. The first section compares gene arrangements for different pathways in Pseudomonas aeruginosa PAO1 to determine if the gene arrangements are similar to previous studies. It also serves as a reference for pyrimidine gene arrangements in P. aeruginosa. The second part compares the physical, and genetic maps of P. aeruginosa PAO1 with the genome sequence. The final section compares pyrimidine gene arrangements in three species of Pseudomonas. Pyrimidine biosynthesis and salvage genes will be aligned for P. aeruginosa PAO1, P. putida KT2440, and P. syringae DC3000. The whole study will gives insight into gene patterns in Pseudomonas, with a focus on pyrimidine genes.
- Structure-Function Studies on Aspartate Transcarbamoylase and Regulation of Pyrimidine Biosynthesis by a Positive Activator Protein, PyrR in Pseudomonas putida
- The regulation of pyrimidine biosynthesis was studied in Pseudomonas putida. The biosynthetic and salvage pathways provide pyrimidine nucleotides for RNA, DNA, cell membrane and cell wall biosynthesis. Pyrimidine metabolism is intensely studied because many of its enzymes are targets for chemotheraphy. Four aspects of pyrimidine regulation are described in this dissertation. Chapter I compares the salvage pathways of Escherichia coli and P. putida. Surprisingly, P. putida lacks several salvage enzymes including nucleoside kinases, uridine phosphorylase and cytidine deaminase. Without a functional nucleoside kinase, it was impossible to feed exogenous uridine to P. putida. To obviate this problem, uridine kinase was transferred to P. putida from E. coli and shown to function in this heterologous host. Chapter II details the enzymology of Pseudomonas aspartate transcarbamoylase (ATCase), its allosteric regulation and how it is assembled. The E. coli ATCase is a dodecamer of two different polypeptides, encoded by pyrBI. Six regulatory (PyrI) and six catalytic (PyrB) polypeptides assemble from two preformed trimers (B3) and three preformed regulatory dimers (I2) in the conserved 2B3:3I2 molecular structure. The Pseudomonas ATCase also assembles from two different polypeptides encoded by pyrBC'. However, a PyrB polypeptide combines with a PyrC. polypeptide to form a PyrB:PyrC. protomer; six of these assemble into a dodecamer of structure 2B3:3C'2. pyrC' encodes an inactive dihydroorotase with pyrB and pyrC' overlapping by 4 bp. Chapter III explores how catabolite repression affects pyrimidine metabolism. The global catabolite repression control protein, Crc, has been shown to affect pyrimidine metabolism in a number of ways. This includes orotate transport for use as pyrimidine, carbon and nitrogen sources. Orotate is important because it interacts with PyrR in repressing the pyr genes. Chapter IV describes PyrR, the positive activator of the pyrimidine pathway. As with other positive activator proteins, when pyrimidine nucleotides are depleted, PyrR binds to …