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Functional and Categorical Analysis of Waveshapes Recorded on Microelectrode Arrays

Description: Dissociated neuronal cell cultures grown on substrate integrated microelectrode arrays (MEAs) generate spontaneous activity that can be recorded for up to several weeks. The signature wave shapes from extracellular recording of neuronal activity display a great variety of shapes with triphasic signals predominating. I characterized extracellular recordings from over 600 neuronal signals. I have preformed a categorical study by dividing wave shapes into two major classes: (type 1) signals in which the large positive peak follows the negative spike, and (type 2) signals in which the large positive peak precedes the negative spike. The former are hypothesized to be active signal propagation that can occur in the axon and possibly in soma or dendrites. The latter are hypothesized to be passive which is generally secluded to soma or dendrites. In order to verify these hypotheses, I pharmacologically targeted ion channels with tetrodotoxin (TTX), tetraethylammonium (TEA), 4-aminopyridine (4-AP), and monensin.
Date: May 2005
Creator: Schwartz, Jacob C.

Functional Characterization of Mtnip/latd’s Biochemical and Biological Function

Description: Symbiotic nitrogen fixation occurs in plants harboring nitrogen-fixing bacteria within the plant tissue. The most widely studied association is between the legumes and rhizobia. In this relationship the plant (legumes) provides the bacteria (rhizobia) with reduced carbon derived from photosynthesis in exchange for reduced atmospheric nitrogen. This allows the plant to survive in soil, which is low in available of nitrogen. Rhizobia infect and enter plant root and reside in organs known as nodules. In the nodules the bacteria fix atmospheric nitrogen. The association between the legume, Medicago truncatula and the bacteria Sinorhizobium meliloti, has been studied in detail. Medicago mutants that have defects in nodulation help us understand the process of nitrogen fixation better. One such mutant is the Mtnip-1. Mtnip-1 plants respond to S. meliloti by producing abnormal nodules in which numerous aberrant infection threads are produced, with very rare rhizobial release into host plant cells. The mutant plant Mtnip-1 has an abnormal defense-like response in root nodules as well as defects in lateral root development. Three alleles of the Mtnip/latd mutants, Mtnip-1, Mtlatd and Mtnip-3 show different degrees of severity in their phenotype. Phylogenetic analysis showed that MtNIP/LATD encodes a protein belonging to the NRT1(PTR) family of nitrate, peptide, dicarboxylate and phytohprmone transporters. Experiments with Mtnip/latd mutants demonstrats a defective nitrate response associated with low (250 μM) external nitrate concentration rather than high (5 mM) nitrate concentration. This suggests that the mutants have defective nitrate transport. To test if MtNIP/LATD was a nitrate transporter, Xenopus laevis oocytes and Arabidopsis thaliana mutant plants Atchl1-5, defective in a major nitrate transporter AtNRT1.1(CHL1), were used as surrogate expression systems. Heterologous expression of MtNIP/LATD in X. laevis oocytes and Atchl1-5 mutant plants conferred on them the ability to take up nitrate from external media with high affinity, thus demonstrating that MtNIP/LATD ...
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Date: December 2013
Creator: Bagchi, Rammyani

Functional Characterization of Plant Fatty Acid Amide Hydrolases

Description: Fatty acid amide hydrolase (FAAH) terminates the endocannabinoid signaling pathway that regulates numerous neurobehavioral processes in animals by hydrolyzing a class of lipid mediators, N-acylethanolamines (NAEs). Recent identification of an Arabidopsis FAAH homologue (AtFAAH) and several studies, especially those using AtFAAH overexpressing and knock-out lines suggest that a FAAH-mediated pathway exists in plants for the metabolism of endogenous NAEs. Here, I provide evidence to support this concept by identifying candidate FAAH cDNA sequences in diverse plant species. NAE amidohydrolase assays confirmed that several of the proteins encoded by these cDNAs indeed catalyzed the hydrolysis of NAEs in vitro. Kinetic parameters, inhibition properties, and substrate specificities of the plant FAAH enzymes were very similar to those of mammalian FAAH. Five amino acid residues determined to be important for catalysis by rat FAAH were absolutely conserved within the plant FAAH sequences. Site-directed mutation of each of the five putative catalytic residues in AtFAAH abolished its hydrolytic activity when expressed in Escherichia coli. Contrary to overexpression of native AtFAAH in Arabidopsis that results in enhanced seedling growth, and in seedlings that were insensitive to exogenous NAE, overexpression of the inactive AtFAAH mutants showed no growth enhancement and no NAE tolerance. However, both active and inactive AtFAAH overexpressors displayed hypersensitivity to ABA, suggesting a function of the enzyme independent of its catalytic activity toward NAE substrates. Yeast two-hybrid screening identified Arg/Ser-rich zinc knuckle-containing protein as a candidate protein that physically and domain-specifically interacts with AtFAAH and its T-DNA knock-out Arabidopsis was hypersensitive to ABA to a degree similar to AtFAAH overexpressors. Taken together, AtFAAH appears to have a bifurcating function, via NAE hydrolysis and protein-protein interaction, to control Arabidopsis growth and interaction with phytohormone signaling pathways. These studies help to functionally define the group of enzymes that metabolize NAEs in plants, and further will ...
Date: December 2010
Creator: Kim, Sang-Chul

Functional Neural Toxicity and Endocrine Responses in Mice Following Naphthalene Exposure

Description: Polycyclic aromatic hydrocarbons (PAHs) are a well studied and diverse class of environmental toxicants. PAHs act via the aryl hydrocarbon receptor (AhR), and studies have suggested that PAHs may elicit neurological and estrogenic effects. Doses of PAHs between 50 to 150 ppm may elicit neurotoxicity in rodent models. The present study investigated the effects of naphthalene on in vivo steroidogenesis in Swiss Webster male mice, and in vitro neural function of Balb-C/ICR mice frontal cortex neurons. These data suggest that naphthalene may not elicit steroidogenic effects at concentrations ranging from 0.2 to 25 mg/kg/day, following a 7 day subcutaneous dosing regime. In addition, naphthalene may cause functional toxicity of frontal cortex neurons at concentrations of 32 to 160 ppm naphthalene.
Date: August 2010
Creator: Colbert, Crystal

Functional Properties and Organization of Primary Somatosensory Cortex

Description: The physiological characteristics and organization of cat primary somatosensory cortex (SI) were studied in electrophysiological and anatomical experiments. In single cell recording experiments, quantitatively controlled mechanical stimuli were used to examine the responses of SI cortical neurons to the velocity component of skin or hair displacement. The firing frequency of most rapidly adapting neurons increased as stimulus velocity was increased. Rapidly adapting neurons were classified based on their response patterns to constant-velocity ramp stimuli. Neurons in these classes differed significantly in sensitivity to stimulus velocity and amplitude, adaptation rate, and spontaneous firing rate. The results suggest that frequency coding of stimulus displacement velocity could be performed by individual SI rapidly adapting neurons, and that the classes of rapidly adapting neurons may play different roles in sensation of tactile stimuli. Tract-tracing experiments were used to investigate the ipsilateral corticocortical connections of areas 3b and 2 in SI. Different patterns of connections were found for these areas: area 2 projects to areas 3b, 1, 3a, 5a, 4 and second somatosensory cortex (SII), and area 3b projects to areas 2, 1, 3a and SII. To further compare the organization of these areas, the thalamic input to the forepaw representation within each area was studied. The forepaw region in area 3b receives thalamic input exclusively from ventroposteriopr lateral nucleus (VPL), while area 2 receives input from VPL, medial division of the posterior complex (PoM), and lateral posterior nucleus (LP). These results suggest that area 2 lies at a higher position in the hierarchy of somatosensory information flow.
Date: December 1993
Creator: Esteky, Hossein

GABAᴀ Receptors in Rat Whisker Barrel Cortex: Effects of Sensory Deprivation

Description: The GABAergic system in adult sensory cortex is affected by sensory deprivation, but little is known about how this predominant inhibitory system is affected during ontogeny. The present study investigates developmental effects of whisker trimming on GABAa receptors in rat barrel cortex. Rats trimmed for 6 wk beginning at birth and adulthood showed similar decreases in [3H]muscimol binding in deprived relative to non-deprived barrels, suggesting absence of a critical period.
Date: August 1995
Creator: Salazar, Eduardo, 1962-

Gene Expression Profiling of the nip Mutant in Medicago truncatula

Description: The study of root nodule symbiosis between nitrogen-fixing bacteria and leguminous plant species is important because of the ability to supplement fixed nitrogen fertilizers and increase plant growth in poor soils. Our group has isolated a mutant called nip in the model legume Medicago truncatula that is defective in nodule symbiosis. The nip mutant (numerous infections with polyphenolics) becomes infected by Sinorhizobium meliloti but then accumulates polyphenolic defense compounds in the nodule and fails to progress to a stage where nitrogen fixation can occur. Analysis of the transcriptome of nip roots prior to inoculation with rhizobia was undertaken using Affymetric Medicago Genome Array microarrays. The total RNA of 5-day old uninoculated seedlings was analyzed in triplicate to screen for the NIP gene based on downregulated transcript levels in the mutant as compared to wild type. Further microarray data was generated from 10 days post inoculation (dpi) nip and wild type plants. Analysis of the most highly downregulated transcripts revealed that the NIP gene was not identifiable based on transcript level. Putative gene function was assigned to transcripts with altered expression patterns in order to characterize the nip mutation phenotypically as inferred from the transcriptome. Functional analysis revealed a large number of chaperone proteins were highly expressed in the nip mutant, indicating high stress in the mutant prior to infection by rhizobia. Additionally, a database containing the information regarding the nip expression profile at both 0 days post inoculation (dpi) and 10 dpi were created for screening of candidate genes as predicted from sequence in the genomic region containing NIP.
Date: August 2007
Creator: McKethan, Brandon Lee

Gene Flow among Populations of the Mayfly Epeorus pleuralis (Banks 1910) (Ephemeroptera: Heptageniidae) in Three Adjacent Appalachian Headwater Streams

Description: Dispersal of aquatic insects is difficult to measure with traditional direct trapping methodologies. However, genetic markers are an ideal surrogate to indirectly infer dispersal and gene flow. For this research, a portion of the cytochrome oxidase I gene was used to evaluate gene flow and dispersal of Epeorus pleuralis located in the northern Appalachian headwater streams of the Allegheny, Genesee, and Susquehanna watersheds. A total of 536 basepairs from 16 individual insects were used for analysis. Thirteen haplotypes were discovered, two of which were shared between the Allegheny and Genesee streams. Although no shared haplotypes were found in the Susquehanna, analysis of molecular variance results suggest that there is not a significant genetic difference between the three populations and attributes the majority of variation to within population differences.
Date: May 2006
Creator: Dunlap, Rebecca

Generating Molecular Biology Tools to Investigate the Ca2+ Binding Ability of Arabidopsis TON2

Description: The position of the cell division plane in plants is determined by the position of the preprophase band. The pre prophase band (PPB) is a ring of microtubules centered around the nucleus on the inner side of plasma membrane that establishes the cortical division site. The PPB forms at the end of G2 and breaks down at the end of prophase leaving behind protein markers of its position that are collectively called the cortical division site. During cytokinesis the phragmoplast expands towards the cortical division site and mediates the fusion of the new cell plate with the mother cell at that position. Several proteins necessary for PPB formation in plants have been identified, including maize DCD1 and ADD1 and Arabidopsis TON2, which are all type 2A protein phosphatase (PP2A)B" regulatory subunits. DCD1, ADD1, and TON2 localize to the PPB and the cortical division site through metaphase. The PP2A subunits each have two EF-hand domains, which are predicted to bind calcium ions. Since calcium ions are important for some aspects of cell division, we designed a series of constructs to test if TON2 binds calcium. TON2 protein was cloned into expression vectors, pET42a, and expression of TON2 protein was confirmed via Western blotting and immunodetection using a GST antibody. Site directed mutagenesis was used to mutate the TON2 EF-hand domains and mutated cDNAs were also cloned into expression vectors. These were then expressed in bacterial systems. Finally, the GST tagged proteins were purified. In the future, wild-type and mutated proteins TON2 proteins will used in calcium binding assays to determine if TON2 binds calcium.
Date: August 2017
Creator: Shao, Danyang

Genetic Analysis of Development and Behavior in Hypoxia and Cellular Characterization of Anoxia Induced Meiotic Prophase Arrest in Caenorhabditis Elegans

Description: It was hypothesized that chronic hypoxia will affect various biological processes including developmental trajectory and behavior. To test this hypothesis, embryos were raised to adulthood in severe hypoxic environments (0.5% O2 or 1% O2, 22°C) and analyzed for survival rate, developmental progression, and altered behaviors. Wildtype hermaphrodites survive chronic hypoxia yet developmental trajectory is slowed. The hermaphrodites raised in chronic hypoxia had different phenotypes in comparison to the normoxic controls. First, hermaphrodites exposed to chronic hypoxia produced a significantly lower number of embryos and had a slight increase in male progeny. This suggests that chronic hypoxia exposure during development affects the germline. Second, animals raised in chronic hypoxia from embryos to young adults have a slight increase in lifespan when re-exposed to a normoxic environment, indicating that chronic hypoxia does not negatively decrease lifespan. Finally, hermaphrodites that were raised in hypoxia will lay the majority of their eggs on the area of the agar plate where the bacterial lawn is not present. This is in contrast to animals in normoxia, which lay the majority of their eggs on the bacterial lawn. One hypothesis for this hypoxia-induced egg-laying behavior is that the animal can sense microenvironments in hypoxia. To examine if various pathways are involved with chronic-hypoxia responses RNAi and assayed genetic mutants were used. Specifically, genetic mutations affecting oxygen sensing (egl-9), aerotaxis (npr-1), TFG-ß signaling (dbl-1, daf-7) and predicted oxygen-binding proteins (globin-like genes) were phenotypically analyzed. Results indicate that mutations in several of these genes (npr-1, dbl-1) resulted in a decrease in hypoxia survival rate. A mutation in egl-9 also had a detrimental affect on the viability of an animal raised in chronic hypoxia. However, a similar phenotype was not observed in the vhl-1 mutation indicating that the phenotype may not be due to a mere increase in HIF-1 levels, ...
Date: August 2011
Creator: Little, Brent Ashley

Genetic and Cellular Analysis of Anoxia-Induced Cell Cycle Arrest in Caenorhabditis elegans

Description: The soil-nematode Caenorhabditis elegans survives oxygen deprivation (anoxia < 0.001 kPa of O2, 0% O2) by entering into a state of suspended animation during which cell cycle progression at interphase, prophase and metaphase stage of mitosis is arrested. I conducted cell biological characterization of embryos exposed to various anoxia exposure times, to demonstrate the requirement and functional role of spindle checkpoint gene san-1 during brief anoxia exposure. I conducted a synthetic lethal screen, which has identified genetic interactions between san-1, other spindle checkpoint genes, and the kinetochore gene hcp-1. Furthermore, I investigated the genetic and cellular mechanisms involved in anoxia-induced prophase arrest, a hallmark of which includes chromosomes docked at the nuclear membrane. First, I conducted in vivo analysis of embryos carried inside the uterus of an adult and exposed to anoxic conditions. These studies demonstrated that anoxia exposure prevents nuclear envelope breakdown (NEBD) in prophase blastomeres. Second, I exposed C. elegans embryos to other conditions of mitotic stress such as microtubule depolymerizing agent nocodazole and mitochondrial inhibitor sodium azide. Results demonstrate that NEBD and chromosome docking are independent of microtubule function. Additionally, unlike anoxia, exposure to sodium azide causes chromosome docking in prophase blastomeres but severely affects embryonic viability. Finally, to identify the genetic mechanism(s) of anoxia-induced prophase arrest, I conducted extensive RNA interference (RNAi) screen of a subset of kinetochore and inner nuclear membrane genes. RNAi analysis has identified the novel role of 2 nucleoporins in anoxia-induced prophase arrest.
Date: December 2008
Creator: Hajeri, Vinita A.

Genetic and Environmental Factors that Mediate Survival of Prolonged Oxygen Deprivation in the Nematode Caenorhabditis Elegans

Description: Ischemic events of even a very short duration are not tolerated Ill in humans. The human cost of ischemia, when looked at as combined cardiovascular disease, dwarfs all other causes of death in the United States. Annually, CVD kills as many people in the US as does cancer, chronic lower respiratory disease, accidents, and diabetes mellitus combined. In 2005 (the latest year for which final statistics are available), CVD was responsible for 864,480 deaths or 35.3 percent of total deaths for the year. In my study, I have used the nematode Caenorhabditis elegans to determine genetic and environmental modulators of oxygen deprivation a key component of ischemia. I have found that animals with mutations in insulin like signaling pathways, neuronal function, electron transport chain components, germline function, and animals that are preconditioned by being raised on a diet of E. coli HT115 bacteria at 25°C have an enhanced ability to survive long-term (>72 hours) anoxia (<.005 kPa O2) at 20°C. The enhanced anoxia survival phenotype partially correlates with increased levels of carbohydrate stores in the nematodes. Suppression of this enhanced anoxia survival phenotype is possible by altering expression of the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase, the FOXO transcription factor DAF-16, and 5’-AMP kinase.
Date: August 2010
Creator: LaRue, Bobby Lee, Jr.

Genetic Characterization of Central and South American Populations of Scarlet Macaw (Ara macao)

Description: The wild populations of the Scarlet Macaw subspecies native to southern Mexico and Central America, A. m. cyanoptera, have been drastically reduced over the last half century and are now a major concern to local governments and conservation groups. Programs to rebuild these local populations using captive bred specimens must be careful to reintroduce the native A. m. cyanoptera, as opposed to the South American nominate subspecies (A. m. macao) or hybrids of the two subspecies. Molecular markers for comparative genomic analyses are needed for definitive differentiation. Here I describe the isolation and sequence analysis of multiple loci from 7 pedigreed A. m. macao and 14 pedigreed A. m. cyanoptera specimens. The loci analyzed include the 18S rDNA genes, the complete mitogenome as well as intronic regions of selected autosomally-encoded genes. Although the multicopy18S gene sequences exhibited 10% polymorphism within all A. macao genomes, no differences were observed between any of the 21 birds whose genomes were studied. In contrast, numerous polymorphic sites were observed throughout the 16,993 bp mitochondrial genomes of both subspecies. Although much of the polymorphism was observed in the genomes of both subspecies, subspecies-specific alleles were observed at a number of mitochondrial loci, including 12S, 16S, CO2 and ND3. Evidence of possible subspecies-specific alleles were also found in three of four screened nuclear loci. Collectively, these mitochondrial and nuclear loci can be used as the basis to distinguish A. m. cyanoptera from the nominate subspecies, A. m. macao, as well as identify many hybrids, and most importantly will contribute to further reintroduction efforts.
Date: May 2016
Creator: Kim, Tracy

Genetic Differentiation of the Geomys Pocket Gopher Complex of Texas

Description: Genetic variation was analyzed for populations of seven taxa comprising four cytotypes of the Geomys bursarius chromosome complex, including G. b. major, G. b. knoxjonesi, and the Edwards Plateau taxa, G. b. llanensis and G. b. texensis. Genetic relationships of the Edwards Plateau gophers with other taxa and between themselves were examined. Genetic similarity, number of fixed allelic differences, and ectoparasite distribution indicate the Edwards Plateau gophers are a distinct gene pool. Isolation of the Edwards Plateau taxa precludes contact zone analysis. However, genetic differentiation is typical of that between other species of Geomys, and the Edwards Plateau taxa should be recognized as G. texensis. Distributions of allelic frequencies indicate little justification in retaining the subspecific status of the Edwards Plateau forms.
Date: August 1988
Creator: Block, Scott B. (Scott Bishop)

Genetic Mechanisms for Anoxia Survival in C. Elegans

Description: Oxygen deprivation can be pathological for many organisms, including humans. Consequently, there are several biologically and economically relevant negative impacts associated with oxygen deprivation. Developing an understanding of which genes can influence survival of oxygen deprivation will enable the formulation of more effective policies and practices. In this dissertation, genes that influence adult anoxia survival in the model metazoan system, C. elegans, are identified and characterized. Insulin-like signaling, gonad function and gender have been shown to influence longevity and stress resistance in the soil nematode, C. elegans. Thus, either of these two processes or gender may influence anoxia survival. The hypothesis that insulin-like signaling alters anoxia survival in C. elegans is tested in Aim I. The hypotheses that gonad function or gender modulates anoxia survival are tested in Aim II. Insulin-like signaling affects anoxia survival in C. elegans. Reduction of insulin-like signaling through mutation of the insulin-like receptor, DAF-2, increases anoxia survival rates in a gpd-2/3 dependent manner. The glycolytic genes gpd-2/3 are necessary for wild-type response to anoxia, and sufficient for increasing anoxia survival through overexpression. Gonad function and gender both affect anoxia survival in C. elegans. A reduction of ovulation and oocyte maturation, as measured by oocyte flux, is associated with enhanced anoxia survival in all cases examined to date. Reduction of function of several genes involved in germline development and RTK/Ras/MAPK signaling reduce ovulation and oocyte maturation while concurrently increasing anoxia survival. The act of mating does not influence anoxia survival, but altering ovulation through breeding or chemical treatment does. The male phenotype also increases anoxia survival rates independent of genotype. These studies have identified and characterized over ten different genotypes that affect adult survival of anoxia in C. elegans. Before these studies were conducted, there were no genes known to influence adult anoxia survival in C. ...
Date: August 2008
Creator: Mendenhall, Alexander R.

Genetic Modification of Fatty Acid Profiles in Cotton

Description: The industrial uses of cottonseed oil are limited by its fatty acid composition. Genetic modification of cotton lipid profiles using seed-specific promoters could allow cotton growers to produce valuable new oils in the seed without adverse effects on fiber quality and yield, therefore making this crop more commercially profitable. Transgenic cotton callus harboring a diverged fatty acid desaturase gene (FADX) from Momordica charantia was characterized for production of alpha-eleostearic acid (conjugated double bonds: 18:3 D9 cis, 11 trans, 13 trans), not normally found in cotton. Gas chromatography (GC) in conjunction with mass spectrometry (MS) confirmed production of alpha-eleostearic acid in the transgenic cotton tissues. A second series of transformation experiments introduced the cotton fatty acid thioesterase B (FATB) cDNA, fused to the seed-specific oleosin promoter into cotton to promote the over-expression of FATB, to generate cotton with increased palmitate in the cottonseed. PCR amplification, as well as fatty acid analysis by gas chromatography, confirmed introduction of the FATB cDNA in transgenic tissues. Collectively, these results demonstrate the feasibility of manipulating the fatty acid composition in cotton via transgenic approaches and form the basis for continued efforts to create novel oils in cottonseed.
Access: This item is restricted to the UNT Community Members at a UNT Libraries Location.
Date: August 2005
Creator: Rommel, Amy A.

The Genetics of Pigmentation in Corynebacterium poinsettiae ATCC 9682

Description: Corynebacterium poinsettiae mutant strains blocked in carotenoid biosynthesis were obtained by treatment with the mutagen N-methyl-N1-nitro-N-nitrosoguanidine. Additional carotenoid (Crt) mutant strains were obtained from a previous study conducted in our laboratory. Fifty-nine Crt mutants affected in carotenoid biosynthesis were examined by a normal phase high performance liquid chromatography (HPLC) system. Pigment extracts of Crt mutants and C. poinsettiae wild type strains were resolved by an isocratic system with hexane:acetone:dicholoromethane, 11.35:1.73:1.00 (by vol.) as the eluting solvent. In addition to the five major peaks, twelve minor peaks were observed in the wild type C. poinsettiae strain used in this study. Crt mutant and wild type strain peak heights were measured from the individual chromatograms and the peak height data set created was analyzed using the Statistical Analysis System program to perform a cluster analysis. The cluster analysis revealed five carotenoid mutant groups. Carotenoid pigments which accumulated or were absent in each of the cluster groups are reported. Cluster group 1 mutants (CrtA) are blocked in the dehydrogenase(s) which is(are) responsible for the dehydrogenations between phytoene and lycopene. Cluster group 2 mutants (CrtB) appear to be blocked at a second dehydrogenase specific for the dehydrogenation from C.p. 470 to C.p. 496. Cluster group 3 mutants (CrtC) are blocked at a cyclization step in the pathway which involves cyclization of C.p. 496 to C.p. 470 and which may cyclize C.p. 473 to C.p. 450. The genes CrtA and CrtB map only 0.5 map units from each other while CrtA and CrtC map 2.1 map units from one another. Mutants which accumulate end products but which lack certain precursors indicate a branched pathway for pigment biosynthesis exists in this organism. Media for the formation, fusion and regeneration of C. poinsettiae protoplasts are reported and a protocol for the use of these media in genetic ...
Date: August 1986
Creator: Campbell, Alan L. (Alan Lee)

Genic Differentiation and Evolution in the Ground Squirrel Subgenus Ictidomys (Spermophilus)

Description: The genetic structure of 26 natural populations of three species (S. tridecemlineatus, S. mexicanus, and S. spilosoma) of the Ictidomys subgenus of ground squirrels was analyzed using chromosomal and electrophoretic techniques. Chromosomal variation was not observed in S. mexicanus, and only slight karyotypic variation was found in the other two species. Chromosomal evidence indicated hybridization between S. tridecemlineatus and S. mexicanus, placing these species within the classical definition of semispecies. Analysis of electrophoretic variation at 29 genetic loci indicated close genetic relationships between these species. Evolution in Ictidomys appears to be linked with Pleistocene events, and speciation appears to have occurred within the last 155,000 years.
Date: December 1975
Creator: Cothran, E. Gus, 1951-

Genic Differentiation Between Two Chromosomal Races of Pocket Gophers, Geomys bursarius

Description: Genic data from two chromosomal races of Geomys bursarius from a contact zone in central Texas indicated that the two races possessed distinct gene pools which would define them as separate species. Data from proteins encoded from 21 loci in this study substantiated this hypothesis. A pattern of alternately fixed alleles at the ADH-l, MDH-2, LDH-l, and IDH-1 loci with no apparent gene flow in zones of contact strongly suggested that these two races should be designated as separate species. Levels of heterozygosity and high FST values indicate that genomic structuring within Geomys is most heavily influenced by high levels of inbreeding and low migration rates. Fossorial rodents were suggested to undergo speciation primarily through parapatric means.
Date: May 1980
Creator: Bohlin, Raymond G.

Glucose and Altered Ceramide Biosynthesis Impact the Transcriptome and the Lipidome of Caenorhabditis elegans

Description: The worldwide rise of diabetes and obesity has spurred research investigating the molecular mechanisms that mediate the deleterious effects associated with these diseases. Individuals with diabetes and/or obesity are at increased risk from a variety of health consequences, including heart attack, stroke and peripheral vascular disease; all of these complications have oxygen deprivation as the central component of their pathology. The nematode Caenorhabditis elegans has been established as a model system for understanding the genetic and molecular regulation of oxygen deprivation response, and in recent years methods have been developed to study the effects of excess glucose and altered lipid homeostasis. Using C. elegans, I investigated transcriptomic profiles of wild-type and hyl-2(tm2031) ( a ceramide biosynthesis mutant) animals fed a standard or a glucose supplemented diet. I then completed a pilot RNAi screen of differentially regulated genes and found that genes involved in the endobiotic detoxification pathway (ugt-63 and cyp-25A1) modulate anoxia response. I then used a lipidomic approach to determine whether glucose feeding or mutations in the ceramide biosynthesis pathway or the insulin-like signaling pathway impact lipid profiles. I found that gluocose alters the lipid profile of daf-2(e1370) (an insulin-like receptor mutant) animals. These studies indicate that a transcriptomic approach can be used to discover novel pathways involved in oxygen deprivation response and further validate C. elegans as a model for understanding diabetes and obesity.
Date: August 2016
Creator: Ladage, Mary Lee

Glucose Induces Sensitivity to Oxygen Deprivation and Alters Gene Expression in Caenorhabditis Elegans

Description: An organisms’ diet represents an exogenous influence that often yields colossal effects on long-term health and disease risk. The overconsumption of dietary sugars for example, has contributed to significant increases in obesity and type-2 diabetes; health issues that are costly both economically and in terms of human life. Individuals who are obese or are type-2 diabetic often have compromised oxygen delivery and an increased vulnerability to oxygen-deprivation related complications, such as ischemic strokes, peripheral arterial disease and myocardial infarction. Thus, it is of interest to identify the molecular changes glucose supplementation or hyperglycemia can induce, which ultimately compromise oxygen deprivation responses. By utilizing the Caenorhabditis elegans genetic model system, which is anoxia tolerant, I determined that a glucose-supplemented diet negatively impacts responses to anoxia and that the insulin-like signaling pathway, through fatty acid and ceramide biosynthesis and antioxidant activity, modulates anoxia survival. Additionally, a glucose-supplemented diet induces lipid accumulation. Use of RNA-sequencing analysis to compare gene expression responses in animals fed either a standard or glucose-supplemented diet revealed that glucose impacts the expression of genes involved with multiple cellular processes including lipid and carbohydrate metabolism, stress responses, cell division, and extracellular functions. Several of the genes we identified are homologous to human genes that are differentially regulated in response to metabolic diseases, suggesting that there may be conserved gene expression responses between C. elegans supplemented with glucose and a diabetic and/or obese state observed in humans. These findings support the utility of C. elegans to model specific aspects of the T2D disease process (e.g., glucose-induced sensitivity to oxygen deprivation) and identify potentially novel regulators of common complications seen in hyperglycemic and T2D patients (e.g., macrovascular complications).
Date: August 2015
Creator: Garcia, Anastacia M.

Green Improvements: A Consumer's Guide to Environmentally and Economically Responsible Home Repairs and Improvements for the North Central Texas Region

Description: The Consumer's Guide is designed to help consumers by providing guidelines for the purchase of specific energy-efficient household appliances- water heaters, air conditioning and heating systems, windows, dishwashers, refrigerators, clothes washers, and dryers. This serves two major purposes: to decrease the environmental impact of those products and to save consumers money over the lifetime of the products. The seven major appliances covered in this work are things that consumers tend to purchase quickly when their older models wear out and with little research into their energy and/or water efficiency. The guide begins with a general introduction and an explanation of the need for energy conservation. Explanations of how they work, purchasing tips, installation tips, maintenance tips, tips for additional energy efficiency, and case studies are given for each appliance. Printable pamphlets are included at the end.
Date: August 2004
Creator: Dickason, Deborah

The Growth of Azotobacter vinelandii on p-Hydroxybenzoic Acid from Soil Medium

Description: The purpose of this study was to search for the substrates utilized by Azotobacter vinelandii in dialysed soil media. Also, we sought to determine the relationship between these substrates and the growth and morphological variations of A. vinelandii. p-Hydroxybenzoic acid was shown to be used as the carbon and energy source by A. vinelandii in dialysed soil medium. The amount of this compound in the soil dialysed soil medium ranged from 14 to 21 micrograms per gram of soil. In a dialysed soil medium, p-hydroxybenzoic acid induced A. vinelandii to form minute bodies, similar to the filtrable forms reported by Gonzalez and Vela, although no growth of minute bodies was detected.
Date: August 1982
Creator: Wu, Fang Jy

A Habitat Evaluation and Management Plan for a Riparian Ecosystem

Description: Ecological research involving habitat studies was conducted on the Elm Fork of the Trinity River in Denton County, Texas, from spring 1985 to spring 1986. Habitat Evaluation Procedures and Habitat Suitability Index Models developed by the United States Fish and Wildlife Service were applied to a 1419 hectares study area to determine the quality of habitat for four species: beaver, Castor canadensis, wood duck, Aix sponsa, pileated woodpecker, Dryocopus pileatus, and white crappie, Poxomis annularis. Population estimates were generated. A wildlife management plan was developed for the study area. Habitat Suitability Index Models were found to be overly conservative, underestimating the quality of habitat in areas of ecological transition.
Date: May 1988
Creator: Wilkinson, Robert N.