UNT Theses and Dissertations - 82 Matching Results

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Evaluation of virulence in wild type and pyrimidine auxotrophs of Pseudomonas aeruginosa using the eukaryotic model system Caenorhabditis elegans.

Description: The human opportunistic pathogen, Pseudomonas aeruginosa PAO1, has been shown to kill the nematode Caenorhabditis elegans. C. elegans has been a valuable model for the study of bacterial pathogenesis, and has reinforced the notion that common virulence and host defense mechanisms exist. Recently, the pyrimidine pathway was shown to regulate virulence levels. Therefore, mutations in the pyrimidine pathway of PAO1 showed decrease virulence in the nematode. When starving the nematode, bacterial resistance was also shown to increase. It was hypothesized that starvation induced the DAF pathway, which regulates the transcription of genes involved with the antibacterial defense mechanism. Further research will be conducted to test this theory by performing RNAi experiments for the genes functioning in the antibacterial defense mechanism.
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Date: August 2004
Creator: Anvari, Sara
Partner: UNT Libraries

Inquiry-based science for high school students: a forensic unit

Description: This project constitutes an instructional unit for honors biology that involves the use of science in the field of criminal investigation and forensics. Before beginning the unit, the learners should have mastered basic laboratory skills, including use of the microscope. They should also have an understanding of the basic structure and function of DNA and its role in heredity and protein synthesis. The standard time frame is 24 days with 70-minute periods, but can be easily adjusted to meet classroom needs. Several instructional strategies enhance student learning and make science fun. The unit is inquiry-driven and activity-based. Students are surprised by the crime, gather and analyze evidence, and work towards proposing an explanation. This real world problem involves the use of cooperative learning and a variety of assessment techniques.
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Date: August 2000
Creator: Apple, Kendra Kea
Partner: UNT Libraries

Effector Response of the Aspartate Transcarbamoylase From Wild Type Pseudomonas Putida and a Mutant with 11 Amino Acids Deleted at the N-terminus of PyrB.

Description: Like its enteric counterpart, aspartate transcarbamoylase (ATCase) from Pseudomonas putida is a dodecamer of two different polypeptides. Unlike the enterics, the Pseudomonas ATCase lacks regulatory polypeptides but employs instead inactive dihydroorotases for an active dodecamer. Previous work showed that PyrB contains not only the active site but also the effector binding sites for ATP, UTP and CTP at its N-terminus. In this work, 11 amino acids were deleted from the N-terminus of PyrB and the ATCase with the truncated protein was expressed in E. coli pyrB- and purified. The wild type enzyme was similarly treated. Velocity-substrate plots without effectors gave Michaelis-Menten kinetics in all cases. Deleting 11 amino acids did not affect dodecameric assembly but altered effector responses. When carbamoylphosphate was varied, the mutant enzyme was inhibited by UTP while the wild type enzyme was activated 2-fold. When the aspartate was varied, CTP had no effect on the mutant enzyme but strongly inhibited the wild type enzyme.
Date: May 2002
Creator: AsFour, Hani
Partner: UNT Libraries

Pyrimidine Enzyme Specific Activity at Four Different Phases of Growth in Minimal and Rich Media, and Concomitant Virulence Factors Evaluation in Pseudomonas aeruginosa

Description: Pseudomonas aeruginosa is a Gram-negative rod, aerobic, non-fermenting, oxidase positive, pigment producing, and nutritionally versatile bacterium. Infections by P. aeruginosa are the most important cause of morbidity and mortality in immunocompromised patients, given virulence factor production that suppresses antibiotic therapy and promotes persistent infection. This research is the first comprehensive report of the pyrimidine biosynthetic pathway for all phases of growth in minimal and rich media coupled with the evaluation of virulence factor production of P. aeruginosa in comparison to four other bacterial species (Pseudomonas putida, Pseudomonas fluorescens, Burkholderia cepacia, and Escherichia coli wild-type strains). Cellular growth and passing genetic information to the next generation depend on the synthesis of purines and pyrimidines, the precursors of DNA and RNA. The pyrimidine biosynthetic pathway is essential and found in most organisms, with the exception of a few parasites that depend upon the pyrimidine salvage pathway for growth. Both the pyrimidine biosynthetic and salvage enzymes are targets for chemotherapeutic agents. In our laboratory, research on pyrimidine auxotrophic mutants showed the role of the pyrimidine biosynthetic pathway and its intermediates on P. aeruginosa metabolism and impaired virulence factors production. The present research shows that pyrimidine enzymes are active in all phases of growth, including the production of two forms of ATCase in the late log phase in P. aeruginosa. This finding may be explained by the displacement of the inactive PyrC' by the active PyrC or PyrC2 to form a new and larger pyrBC encoded ATCase. Pseudomonas aeruginosa wild-type appears to produce by far the most virulence factors, haemolysin, iron chelation, rhamnolipid, adherence, and three types of motility (swimming, swarming, and twitching) investigated in this study, when compared to the other four wild-type strains. Growth analysis was carried out as typically done in minimal medium but also in rich medium to simulate conditions ...
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Date: December 2005
Creator: Azad, Kamran Nikkhah
Partner: UNT Libraries

The Developmental Physiology of the Zebrafish: Influence of Environment and Cardiovascular Attributes

Description: Temperature effects on the development of the zebrafish embryos and larvae and adults were examined. It was found that the earlier in development a temperature change was performed on an embryo, the more significant the change in survival and/or subsequent development. Thus, viable temperature ranges for zebrafish widened significantly as development proceeded. Adults reared and bred at 25oC produced embryos that were significantly more successful at the lower range of rearing temperatures compared to embryos produced from adults reared at 28oC. The majority of this study focused on the physiological effects of swim training during development in the zebrafish. The earlier in development the zebrafish larvae were trained, the greater the mortality. Trained free swimming larvae had a significantly higher routine oxygen consumption after 11 days of training, and a higher mass specific routine metabolic rate after 8 and 11 days of training. Trained free swimming larvae consumed significantly less oxygen during swimming and were more efficient at locomotion, compared to control larvae. Training enhanced survival during exposure to extreme hypoxia in all age groups. Performance aspects of training were investigated in attempt to quantify training effects and in most cases, trained fish performed significantly better than controls. As blood vessels formed during development, they decreased in cross sectional area from days two to six. It was also shown that the variability in visual stroke volume measurements could be reduced significantly by using a third dimension in the analysis with a more accurate volume equation. Finally, the ontogeny of cardiac control was evaluated. The adrenergic receptors were the first to respond to pharmacological stimulation but were closely followed by cholinergic pharmacological stimulation a few days later. There was a significant cholinergic tone present in day 15 zebrafish larvae which persisted. Although an adrenergic tone was not documented in this study, ...
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Date: August 2001
Creator: Bagatto, Brian
Partner: UNT Libraries

In vitro Cultures of Morus alba for Enhancing Production of Phytoestrogens

Description: Plant estrogens have long been associated with health benefits. The potential of tissue culture techniques for the production of several secondary metabolites has been known for many years. Tissue cultures stimulate the production or induce the biosynthesis of novel compounds not found in the mature plant. Tissue culture of Morus alba, family Moraceae, is known to contain phytoestrogens, was established on plant-hormone supplemented Murashige and Skoog (MS) medium. Petiole and the stem tissue from mature trees were the best explants for initiation and proliferation of calli. The best callus proliferation was obtained on MS medium containing 1-napthalene acetic acid (1mg/ml) and benzylaminopurine (0.5mg/ml) for M. alba. Comparison of phytoestrogens of Moraceae species from in vivo and in vitro tissue isolation were carried out. The estrogenic activities of callus extracts were assayed in an estrogen-responsive yeast system expressing the human estrogen receptor alpha. Male callus extracts had higher estrogenic activity than male and female extracts from in vivo and in vitro tissues. Isolation and characterization of phytoestrogens from above tissues were carried out using solid phase extraction, high perfomance liquid chromatography and mass spectrometry techniques. Biochanin A, an isoflavonoid, was isolated as one of the compounds in male callus extracts. Biochanin A has been known to have an antiestrogenic acitivity in mammals. Isoflavonoid compounds have been characterized as strong protein tyrosine kinase inhibitors in variety of animal cells. Isoflavones are structurally similar to estradiol, and display agonistic and antagonistic interactions with the estrogen receptor. Isoflavones possess therapeutic and preventive properties such as being used for postmenopausal osteoporosis, breast cancer, and inhibition of tumors.
Date: December 2009
Creator: Bakshi, Vibhu
Partner: UNT Libraries

A morphological study of the avian (Gallus domesticus) ductus arteriosi during hatching.

Description: The ductus arteriosi (DA) are two blood vessels connecting the pulmonary arteries to the descending aorta in the avian embryo. Following hatching, the DA closes, separation of the systemic and pulmonary circulation. I present the morphological changes that occur in the chicken DA during prepipping, internal pipping, external pipping, and hatching. The avian DA consists of two distinct tissue types, a proximal and a distal portion. Histological examination shows developmental differences between the proximal and distal portions of the DA with regard to lumen occlusion, endothelial cells, smooth muscle and elastin. Endothelial cell proliferation begins to occur as early as external pipping, with the lumen almost completely occluded by the 3rd day of post-hatching life. Expression of vascular endothelial growth factor (VEGF) increases in avian endothelial cells during hatching. I provide a morphological timeline of changes in the DA as the chicken develops from embryo to hatchling.
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Date: May 2006
Creator: Belanger, Candace
Partner: UNT Libraries

Evidentiary Value of Condoms: Comparison of Durable Physical and Chemical Characteristics of Condoms

Description: Condom trace evidence must not be overlooked in sexual assault cases; understanding the chemical and physical characteristics of condoms is imperative if condoms are to be useful evidence. Previous research shows that condom identification is possible, but it is equally important to evaluate durability of condom residues versus time. Using FT-IR, this study examined vaginal swabs from subjects who self-sampled at intervals for up to 72 hours after having intercourse with a condom. This study investigated whether age and the stage of the menstrual cycle affected the durability of residues in the vagina over time. This study revealed that condoms containing nonoxynol-9, silicone-based lubricants, and particulates provide valuable information for identification, and that nonoxynol-9 specifically withstands the vaginal environment for up to 72 hours. Additionally, age and menstrual cycle both appeared to have an effect on the durability of residues although larger sample size is desirable.
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Date: May 2000
Creator: Belcher, Kelly Leigh
Partner: UNT Libraries

Establishing genetic and physiological baselines for the black-tailed prairie dog (Cynomys ludovicianus).

Description: The black-tailed prairie dog (Cynomys ludovicianus) has experienced dramatic declines over much of its historical range due to habitat loss, plague, poisonings, and shootings. Many populations now occur as isolated genetic relicts. A multiple locus genetic profile was obtained using microsatellite analyses of six polymorphic nucleotide repeats from 319 black-tailed prairie dogs collected from 16 colonies throughout the state of Texas. This assessment revealed that existing populations have sufficient variation at all six loci to verify the usefulness of this approach as a primary genetic tool in conservation and preservation. The data reveals regional-dependent frequency patterns as well as support for founder/bottleneck effects for several of the 16 sites. Although the prairie dog population in Texas as a whole may appear genetically diverse, considerable genetic divergence has already occurred among the subpopulations (FST = 0.164). Isolation by distance is supported by genic differentiation analysis (P < 0.001) and pairwise correlation analysis between genetic distance and geographic distance (P < 0.001). Prairie dogs from six (COC, LUBA, LUBC, LUBD, LUBE, and TAR) of the original 16 sites have been relocated or exterminated, or were in the process of being relocated. Results indicated the following colonies (COT, DAL, HOW, and HUD) are of sufficient size and possess ample genetic diversity to be characterized as candidate foundation populations for future preservation efforts. The proximity of small colonies (< 20 hectares) such as HEMB, LUBB, and PEC, to other colonies should be examined to determine if they are isolated or part of a metapopulation. Colonies (HAR, HEMA, and SCH) with low genetic diversity would be ideal candidates for supplementation. Alternatively, these colonies could be relocated or blended with other similar but genetically distinct colonies. Baselines for healthy, pet prairie dog hematology and blood chemistries were also established. Results signify that data gathered from pet ...
Date: May 2007
Creator: Biggs, Cindy Dawn
Partner: UNT Libraries

Developmental Patterns of Metabolism and Hematology in the Late Stage Chicken Embryo (Gallus Domesticus) at Two Incubation Temperatures.

Description: 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.
Date: May 2003
Creator: Black, Juli
Partner: UNT Libraries

Cardio-Respiratory Ontogeny and the Transition to Bimodal Respiration in an Air Breathing Fish: Morphological and Physiological Development in Normoxia and Hypoxia.

Description: As selection pressures exist for not only adults, but for every life history stage, it is important to understand how environmental factors shape developing animals. Despite the significance placed on aquatic hypoxia as a driving force in the evolution of air breathing, this is the first known study to examine the effects of hypoxia on cardio-respiratory ontogeny of an air breathing fish. Blue gouramis are obligatory air breathing fish that possess a labyrinth-like structure that serves as the air breathing organ. Gouramis were reared for up to 90 d in normoxia or hypoxia, and morphological and physiological development was observed. Hypoxic larvae had increased lamellar and labyrinth organ surface areas. Bradycardia and increased gill ventilation rates were observed when larvae from either rearing group were briefly exposed to hypoxia. Hypoxic larvae also showed a reduced heart rate and gill ventilation rate in the absence of a hypoxic stimulus, possibly indicative of a more comprehensive, long-term respiratory plasticity. The similarity of routine oxygen consumption between rearing groups suggests that metabolic demand did not change for hypoxic larvae, but that they were more efficient at oxygen acquisition. This is further supported by increased resistance time of hypoxic gouramis to extreme hypoxia. The onset of air breathing was between 20 and 25 d post-fertilization, and was not affected by either rearing or exposure environment. It may be that this behavior is associated with the inability of smaller larvae to successfully overcome water surface tension, rather than with the necessity of aerial respiration at this stage. Hypoxia is commonly experienced by most air breathing fishes, and studies of hypoxia-induced developmental effects may provide critical insights into the evolution of air breathing. The studies presented here provide novel data on the plasticity of cardio-respiratory development of an air breathing fish reared in hypoxia, and can ...
Date: August 2009
Creator: Blank, Tara M.
Partner: UNT Libraries

College Freshman Biology Two Semester Course: Integrating Deep Processing Teaching Techniques

Description: Development of a college level freshman biology course was undertaken in response to government reports that American students have fallen behind students of other countries in the area of the sciences. Teaching strategies were investigated to accomplish two objectives, to define essential academic material to include in the course and to investigate teaching techniques that would increase deep processing of the information. An active process that consisted of applying the cognitive information to solving problems or developing answers to questions was defined as critical thinking. Critical thinking was incorporated into the course by the use of case studies.
Date: May 2002
Creator: Blevins, Mary Jean
Partner: UNT Libraries

A Contravention of Established Principles of Interspecific Allometric Metabolic Scaling in Developing Silkworms, Bombyx Mori.

Description: Established interspecific metabolic allometric relationships do not adequately describe the complexity and variable physiological states of developing animals. Consequently, intraspecific allometric relationships of oxygen consumption and carbon dioxide production as a function of body mass; the respiratory quotient; the function of the silk cocoon; and body composition were investigated for each distinct developmental stage of the silkworm, Bombyx mori. Whole animal O2 consumption in Bombyx ranged from 0.00064 + 0.000047 ml O2 .hr-1 at larval instar I to 0.77 + 0.06 ml O2 .hr-1 in pre-pupal, falling to 0.21+ 0.01 ml O2 .hr-1 in the pupae. Those instars having a significant relationship between O2 consumption as a function of body mass, the slope of the line relating O2 consumption to body mass varied between 0.99 and 1.02, while across all instars the slope was 0.82. Developmental allometry should be presented for individual developmental stages because the individual allometric exponents of the stages can be significantly different from the overall allometric exponent throughout development and in some cases, the overall allometric exponent can be a statistical artifact. The first larval instar of Bombyx mori has the lowest cross sectional area of high metabolic tissue of the midgut (27%) and had one of the highest percentages of some metabolically inert tissues (i.e. lipid, 7.5%). Body composition of the first instar does not support the idea that smaller mass animals having the highest O2 consumption are composed of a greater percentage of metabolically active organs when compared to larger animals. However, this developmental stage has the highest percentage of the mitochondrial marker cytochrome oxidase, which correlates well with the high O2 consumption rate of the smaller mass. Therefore, established interspecific principles should not be assumed to function as valid models for intraspecific developmental relationships of metabolism as a function of body mass. Developmental ...
Date: May 2007
Creator: Blossman-Myer, Bonnie
Partner: UNT Libraries

Incubation humidity as an environmental stressor on the osmoregulatory developmental program of the chicken, Gallus gallus domesticus.

Description: Fetal programming results from stressors during fetal development and may influence the occurrence of disease later in life. Maternal nutritional status and/or environment can affect renal development by inducing limited nephron endowment at birth, which results in diseases such as hypertension and coronary heart disease in mammals. Birds are likely to be effective models for this process because, like mammals, they have high pressure cardiovascular systems, mammalian-type nephrons and are homeothermic. This project uses the chicken embryo to explore physiological responses of disrupted hydration state thereby providing insights into renal fetal programming. Under normal conditions the chorioallantoic membrane (CAM) and developing avian kidney work in unison to ensure a proper balance of ions and water within the egg. White leghorn chicken eggs were incubated at 37.5oC±0.5oC and either <35%, 55-60% (normal) or >85% relative humidity. Amniotic fluid serves as the drinking source for the embryo late in development; its composition is important to salt and water homeostasis. High amniotic fluid osmolality increased the blood osmolality for embryos exposed to low humidity incubation thereby indirectly influencing the renal developmental program of the embryos from this group. Indeed estimated filtering capacity was doubled in the low humidity group (6.77 ± 0.43 mm3) compared to normal (4.80 ± 0.33 mm3) and high (3.97 ± 0.30 mm3) humidity groups. The increased filtering capacity seen for those embryos from low humidity may indicate the ability for more efficient recovery of water if similarly stressed as an adult bird. All embryo populations maintained similar oxygen consumption (0.075 ml/min - 0.37 ml/min), hematocrit (15 % - 32 %) and hemoglobin values (4 g/dl - 9 g/dl), thus displaying control over these aspects of the internal environment despite the obvious environmental insult of extreme incubation humidity. These results signify the embryo's immature kidney, along with lower gastrointestinal tract, ...
Date: August 2009
Creator: Bolin, Greta M.
Partner: UNT Libraries

Leaf elemental analysis and growth characteristics of mycorrhizal treated post oak seedlings via particle induced X-ray emission spectroscopy.

Description: Growth and element assimilation was investigated in post oak seedlings exposed to four different treatment combinations of fertilization and ectomycorrhizal inoculation. Element concentration in excised leaves was analyzed via particle induced X-ray emission spectrometry with a 1.8 MeV proton macrobeam. Mean growth was significantly different across the treatment groups as well as mean concentration of Mg, Al, S, K, Ca, Fe, Cu, and Zn. The data suggest that fertilization rather than mycorrhizal inoculation had a stronger influence on plant growth and nutrient uptake. A follow up study was conducted with a 3 MeV microbeam. A 850 μm2 scanned area of a post oak leaf produced topographical maps of 11 elements.
Date: May 2006
Creator: Boling, Blake C.
Partner: UNT Libraries

Use of Geographic Information System and Remote Sensing Technologies to Describe Mosquito Population Dynamics in the Ray Roberts Greenbelt, Denton County, Texas

Description: 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.
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Date: May 2003
Creator: Bolling, Bethany G.
Partner: UNT Libraries

Coelomic Fluid Protein Profile in Earthworms Following Bacterial Challenge.

Description: Proteomic techniques were used to evaluate the protein profile of the earthworm, (Lumbricus terrestris), following a bacterial challenge. One control group received no injection; a second control group received injections of phosphate buffer solution (PBS). The experimental group received injections of PBS containing (Aeromonas hydrophila). After incubation for 12 hours at 20°C, coelomic fluid was collected from each group for analysis by 2-D electrophoresis. There were significant differences in spot appearance and density between control and experimental groups. Sixteen spots showed a two-fold increase in density and 63 showed at least a two-fold decrease in density between samples from control and bacteria-challenged earthworms, respectively, suggesting up- and down-modulation of proteins potentially involved in the earthworm's response to bacterial challenge.
Date: December 2006
Creator: Brooks, Geoffrey Lance
Partner: UNT Libraries

Heart rate and oxygen consumption during the critical prenatal period in chicken embryos (Gallus gallus): Influence of light cues and the onset of pulmonary ventilation.

Description: To examine if a rhythm can be entrained in either heart rate or oxygen consumption in late stage embryos (days 17-19.5) with light as a zeitgeber, chicken embryos were incubated in complete darkness (D:D) and 12:12 light:dark cycle (L:D). Light had no impact on oxygen consumption (390 µL O2∙min-1∙egg-1) but increased heart rate for non-internally pipped embryos (260 to 270 beats∙min-1 during light cycle). Oxygen consumption increased independent of pipping while heart rate increased (255 to 265 beats∙min-1) in D:D embryos due to pipping. A light-induced rhythm or effect occurred in heart rate but not oxygen consumption, suggesting heart rate and oxygen consumption may be uncoupled.
Date: December 2004
Creator: Brown, Jessie W.
Partner: UNT Libraries

Utilization of Corridor Habitat by White-tailed Deer (Odocoileus virginianus) in Denton County, Texas

Description: White-tailed deer (Odocoileus virginianus) (N=15) movements were determined with use of radio telemetry techniques to determine the utilization of corridor habitat on the Lake Ray Roberts Greenbelt Corridor (RRGC) in north central Texas. Home ranges were calculated using three estimation types. Male white-tailed deer tend to have home ranges twice that of female home ranges. Seasonal home ranges were largest during spring (Feb. - April) and fall (Aug. - Oct.) seasons. Males had greater seasonal variation in utilization than females. No statistically significant difference (p=0.24) between white-tailed deer locations when the RRGC experiences heavy human traffic compared to days when there is light human traffic. Linearity indices indicated home ranges less linear than expected (LI = 3.02). The RRGC should be maintained at its current status to provide a variety of vegetational types and protective cover for white-tailed deer and other wildlife of Denton County.
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Date: May 2004
Creator: Bruce, Troy Kenneth
Partner: UNT Libraries

Biogeography of Montane Mammals on the Colorado Plateau and Adjacent Regions

Description: This study identifies the biogeographic factors that structure small mammal communities on mountains of the Colorado Plateau and adjacent regions. Forty six isolated ranges were characterized across a 5-state study area encompassing the Colorado Plateau, including the central high plateaus of Utah and the Basin and Range Province (i.e. the Great Basin and mountains of Arizona and New Mexico). Presence/absence data of 25 montane mammal species were used to explore the interactions between historical and ecological processes affecting local and regional diversity patterns. Multivariate analyses, such as non-metric dimensional scaling, were used to explore factors which influence community composition. Results of these analyses revealed the Colorado River as a significant biogeographic barrier that affects montane mammal community structure. MtDNA cytochrome b sequence variation was analyzed among populations of the long-tailed vole, Microtus longicaudus, sampled from five interior ranges of the Colorado Plateau- Abajo, LaSal, Henry, and Chuska Mts., and Boulder Mountain of the Aquarius Plateau-and analyzed using traditional phylogenetic approaches (parsimony and likelihood) as well as nested clade analysis. Results support previous documentation of a major east-west phylogeographic break occurring between populations southeast of the Colorado River (eastern Arizona, Colorado, Wyoming and New Mexico) and all other western populations, which include a central clade, a northwest clade, and an Alaskan island clade. Evidence also supports differentiation of a 'southern Rockies' clade and a distinct 'southwest island' clade. Populations of M. longicaudus north and west of the Colorado River (Boulder and Henry Mts.) share two haplotypes, form a well-supported subclade with populations from the Kaibab plateau, and are closely related to the Northwest clade. Past approaches to studying montane mammal communities utilizing theory based on island biogeography have overemphasized area and isolation as the only forces structuring insular communities. As a result, there has been a lack of recognition of the ...
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Date: May 2004
Creator: Carr, Carla B.
Partner: UNT Libraries

Spatial and temporal patterns exhibited by select physicochemical and biological water quality parameters in Lake Texoma, Oklahoma and Texas.

Description: From August 1996 through September 1997 eleven fixed stations were sampled monthly in January, March , April , July, August, September, and November and fortnightly in May and June for the purposes of establishing baseline conditions present in Lake Texoma as related to U.S. Army Corps of Engineers chloride control activities in the upper Wichita River, Texas. Five reservoir zones were identified a priori using historical chloride concentration data and include the Red River Zone (RRZ), Red River Transition Zone (RRTZ), Main Lake Body (MLB), Washita River Transition Zone (WRTZ), and Washita River Zone (WRZ) in order of decreasing chloride concentration. The existence of the WRTZ is not supported here, however the Big Mineral Arm in the RRTZ was observed to be highly independent of the mixing patterns observed in the RRTZ and was treated post priori separately from the RRTZ. Spatial and temporal comparisons between reservoir zones were performed on seventeen (17) physicochemical parameters from each of the eleven sampling stations and phytoplankton count data from one sampling station within each reservoir zone and physicochemical parameters were observed to exhibit a fixed spatial gradient. Strong density gradients throughout the reservoir were observed to occur in conjunction with vertical stratification of the water column. Stratification stability at individual stations was attributable to both thermal and salinity density gradients throughout the period of stratification with the degree to which stratification is thermally or chemically induced influenced by inter-annual variability in hydraulic residence time. Hypolimnetic oxygen depletion rates were also observed to be affected by changes in hydraulic residence time with a long-term trend of decreasing relative areal hypolimnetic oxygen rates detected between the 1970s and 1990s. The algal assemblage present in Lake Texoma is dominated by the Cyanophyta, which comprises 82.1 % of the assemblage total standing crop with one species, ...
Date: August 2004
Creator: Clyde, Gerard A.
Partner: UNT Libraries

Mouse cortical cholinergic neurons: Ontogeny of phenotypes in vivo and in vitro.

Description: The development of cholinergic neurons in mouse frontal cortex was studied both in vivo and in vitro by immunocytochemistry with an antibody to choline acetyltransferase (ChAT), the enzyme responsible for acetylcholine synthesis. While cortical cholinergic neurons have previously been characterized in rat cortex, up until very recently, intrinsic cortical cholinergic neurons were considered to be absent in mouse, and little is known about their development or phenotypic characteristics. The present study found no ChAT-positive neurons in mouse frontal cortex on postnatal day 0 (P0, the day of birth). On P7 there were few, faintly stained, ChAT-positive neurons. The numerical density of ChAT-positive neurons increased substantially with age, from none on P0, to 9.2 + 1.4 on P7, to 14.8 + 0.9 on P16, and 41.6 + 3.9 in adulthood. Considering that the numerical density of total neurons decreases during this postnatal period, the data represent a marked developmental increase in the percentage of cholinergic neurons. The development of cholinergic neurons showed very similar timelines in rat and mouse frontal cortex. Cultures prepared from mouse frontal cortex on embryonic day 16 were maintained for 25, 76, or 100 days in vitro (div). The percentage of ChAT-positive neurons was considerably higher than in vivo, ranging from a mean 28% to 31% across the three age (div) groups. With increasing age of the cultures, the numerical density of total neurons and ChAT-positive neurons decreased while the percentage of ChAT-positive neurons did not change significantly. These observations suggest some temporal stability in the cultures. Using dual immunofluorescence, ChAT-positive neurons were tested for colocalization with GAD or TH. The majority of ChAT-positive neurons colocalized with GAD, both in vitro and in vivo. However, ChAT did not colocalize with TH, either in vitro or in vivo. Our comparison of intact frontal cortex and cultures suggest that ...
Date: August 2005
Creator: Coiculescu, Olivia Elena
Partner: UNT Libraries

Hypoxic and hyperoxic incubation affects the ductus arteriosus in the developing chicken embryo (Gallus gallus).

Description: Developing chicken embryos have two ductus arteriosus (DA) that shunt blood away from the lungs and to the chorioallantoic membrane, the embryonic gas exchanger. In mammals, DA closure is stimulated by an increase in blood gas O2 that occurs as the animal begins to breathe with its lungs. The goal of this study was to determine the influence of O2 levels during incubation on the vascular reactivity and morphology of the O2-sensitive DA and to examine the effects of changing O2 levels during late incubation on the morphology of the DA from chicken embryos. In comparison to normoxia, hypoxia (15%) reduced venous O2 levels in day 16 and day 18 embryos and reduced aircell O2 values in day 16, day 18, and internally pipped (IP) embryos, whereas hyperoxia (30%) increased venous O2 levels and aircell O2 level in day 16, day 18, and IP embryos. In comparison to normoxia, hypoxia delayed closure of the DA, whereas hyperoxia accelerated DA closure. In comparison to the left DA from externally pipped (EP) normoxic embryos, the left DA from EP hypoxic embryos exhibited a significantly weaker contractile response to O2. The DA from day 18 hypoxic embryos exhibited a significantly weaker contractile response to norepinephrine and phenylephrine when compared with the DA from day 18 normoxic and hyperoxic embryos. The effect of incubation in hypoxia / hyperoxia during different developmental windows on the DA O2-induced contractile response was observed only in IP embryos that were incubated in normoxia for 16 days and were then moved to hyperoxia. Incubation in hypoxia / hyperoxia resulted in differences in embryo mass, yolk mass, and heart mass. There is an association between the decreased contractile response to O2 and delayed closure in the proximal portion of the DA from hypoxic embryos; as well as an increased contractile ...
Date: December 2009
Creator: Copeland, Jennifer
Partner: UNT Libraries

Application of Cultured Neuronal Networks for Use as Biological Sensors in Water Toxicology and Lipid Signaling.

Description: This dissertation research explored the capabilities of neuronal networks grown on substrate integrated microelectrode arrays in vitro to be applied to toxicological research and lipid signaling. Chapter 1 details the effects of chlorine on neuronal network spontaneous electrical activity and pharmacological sensitivity. This study demonstrates that neuronal networks can maintain baseline spontaneous activity, and respond normally to pharmacological manipulations in the present of three times the chlorine present in drinking water. The findings suggest that neuronal networks may be used as biological sensors to monitor the quality of water and the presence of novel toxicants that cannot be detected by conventional sensors. Chapter 2 details the neuromodulatory effects of N-acylethanolamides (NAEs) on the spontaneous electrical activity of neuronal networks. NAEs are a group of lipids that can mimic the effects of marijuana and can be derived from a variety of plant sources including soy lecithin. The most prominent NAEs in soy lecithin, palmitoylethanolamide (PEA) and linoleoylethanolamide (LEA), were tested individually and were found to significantly inhibit neuronal spiking and bursting activity. These effects were potentiated by a mixture of NAEs as found in a HPLC enriched fraction from soy lecithin. Cannabinoid receptor-1 (CB1-R) antagonists and other cannabinoid pathway modulators indicated that the CB1-R was not directly involved in the effects of NAEs, but that enzymatic degradation and cellular uptake were more likely targets. The results demonstrate that neuronal networks may also be a viable platform for the elucidation of biochemical pathways and drug mechanisms of action.
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Date: August 2004
Creator: Dian, Emese Emöke
Partner: UNT Libraries