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  Partner: UNT Libraries
 Department: Department of Biological Sciences
 Decade: 1990-1999
 Collection: UNT Theses and Dissertations
An Assessment of the Use of Seeding, Mowing, and Burning in the Restoration of an Oldfield to Tallgrass Prairie in Lewisville, Texas
An examination of the effectiveness of seeding, burning, and mowing in the reestablishment of tallgrass prairie species on overgrazed and abandoned pastureland. The study site is a 20 acre tract on U.S. Corps of Engineers land below Lake Lewisville in Denton County, Texas. The site was partitioned into thirty-nine 40 by 40 meter plots with seeding (carried out in 1996) and management treatment (burning, mowing, and no maintenance carried out in 1998) randomly applied following a two level design. For each plot, nine stratified-random 0.1 m2 subplots were examined and shoot counts for each species recorded. The effects of the treatments on individual species and species richness were analyzed with a two-way ANOVA followed by a SNK multiple range test, both on ranked data. Community level analysis was conducted with both a MANOVA on ranked data and a Canonical Correspondence Analysis on raw data. Results indicate that seeding positively affected species richness, particularly when combined with either burning or mowing in the early spring. Mowing also significantly increased species richness in areas that were not seeded, while burning negatively affected species richness on unseeded plots. Treatments significantly affected community composition with treatments having the most clear effect on spring and summer forbs.
Cassette Systems for Creating Intergeneric Hybrid ATCases
Cassette systems for creating intergeneric hybrid ATCases were constructed. An MluI restriction enzyme site was introduced at the carbamoylphosphate binding site within the pyrB genes of both Pseudomonas putida and Escherichia coli. Two hybrids, E. coli pyrB polar domain fused with P. putida pyrB equatorial domain and P. putida pyrB polar domain fused with E. coli pyrB equatorial domain, are possible. The intergeneric E. coli-P. putida hybrid pyrB gene was constructed and found to encode an active ATCase which complemented an E. coli Pyr- strain. These hybrids are useful for kinetic and expression studies of ATCase in E. coli.
Chemotactic Response of Lumbricus terrestris Coelomocytes to Larval and Adult Stages of Rhabditis pellio
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Experiments were performed to assess the suitability of Rhabditis pellio, a nematode found in earthworms, as a challenge organism for use in development of a biomarker assay to determine the potential of chemicals to suppress the immunocompetence of the non-specific immune system. To accomplish this goal, information on the life cycle of R. pellio was determined; including effects of incubation time and temperature on growth rates; along with information on the immune response elicited in the earthworm, Lumbricus terrestris. Immune parameters measured were coelomocyte migration toward and attachment to R. pellio larvae and adults. Preliminary background information showed that R. pellio has potential as a challenge organism for development of a biomarker assay.
Classification of toolmark surfaces on zipper teeth
This study proposes the classification of the toolmark under the heads of zipper teeth as a subclass characteristic as outlined by the Association of Firearm and Toolmark Examiners (AFTE). Two separate cases in which zipper teeth were found at crime scenes prompted this study. Brass zipper teeth manufactured by YKK were taken from 20 pairs of jeans and studied using a Reichert comparison microscope at 4X power. Photographs were taken and over 750 comparisons made. It was found that the toolmarks on each side on the 20 zippers were unique and independent of all other sides. The observations made in this study indicate that classifying zipper teeth toolmarks as a subclass characteristic is valid.
Comparative mitochondrial DNA sequence diversity in isolated and open populations of Southern flying squirrels (Glaucomys volans)
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Three populations of Southern flying squirrels were studied in the Ouachita Mountains of Arkansas to assess the impact of population subdivision-due to island formation--on the population genetics of Glaucomys volans. One island, one mainland, and one open population were investigated. A 367 nucleotide hypervariable region of mitochondrial DNA was sequenced in individuals from each population. Individuals and populations were compared to assess relatedness. Higher sequence diversity was detected in the open and island populations. One island individual shared characters with both the island and mainland populations. Results support the hypothesis that the mainland population may have reduced gene flow. Also, the island population may have been originally founded by at least two maternal lineages.
Development of Cardiovascular Regulation in Embryos of the Domestic Fowl (Gallus Gallus), with a Partial Comparison to Embryos of the Desert Tortoise (Gopherus Agassizii)
In adult vertebrates, cardiovascular regulation is accomplished by numerous systems with neural, hormonal and local components responsible for the majority of regulation. These regulatory components work in concert to maintain the essential function of blood perfusion to adult tissues. Given the essential nature of this function it is therefore surprising that the development of cardiovascular regulation during gestation is poorly understood. The majority of what is known is based on a single vertebrate model, the fetal lamb. The fetal lamb has been used in multiple studies due to the clear clinical applications and has been pivotal in understanding the onset of regulation in developing vertebrates. However, study on the fetal lamb is limited to the latter 40% of gestation and has the added complication of an in-utero developmental strategy. Therefore the primary focus of this dissertation was to characterize basic cardiovascular regulation in the chicken embryo to provided the needed information for it's use an alternative to the fetal lamb. Developing chicken embryos rely on both alpha and beta adrenergic tones to maintain normal heart rate and arterial blood pressure during incubation. However, on day 21, just prior to hatch, these animals lose both tones on arterial pressure suggesting the onset of adult regulation. Cholinergic tone, however, was absent throughout chicken development indicating that it must mature during the neonatal life. Adult cardiovascular reflexes become apparent late in chicken development with a clear baroreflex specifically operating initially on day. However, an adult response to changes in ambient gas tension was absent during incubation suggesting embryos possess unique regulatory systems that are absent in adult chickens. This mechanism is comprised entirely of adrenergic systems with no cholinergic action during change in ambient gas tension. Similar developmental patterns were determined in embryos of the desert tortoise suggesting fundamental differences between in-utero and ex-utero developing vertebrates.
A Multimedia Atlas of Dissection for Comparative Anatomy of the Vertebrates
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Traditional methods of teaching the laboratory course for Comparative Anatomy of the Vertebrates could be improved by applying current computer technology to construct an interactive, multimedial atlas of dissection. Five specimens used in comparative anatomy courses at most institutions were chosen as representative members of the Phylum Chordata: amphioxus, lamprey, dogfish shark, mud puppy, and cat. Specimens were dissected according to the modified method of Wischnitzer, 1993, and each stage was photographed with a Kodak DC120 digital zoom camera. These images were processed on a Power Macintosh 7600 computer with Adobe Photoshop v. 5.0. The atlas was constructed from these images using Macromedia Authorware v. 4.0.3. Each image contains a series of interactive objects that display a highlight and descriptive text as the cursor passes over each object.
Nucleotide Inhibition of Glyoxalase II
The glyoxalase system mediates the conversion of methylglyoxal, a toxic ketoaldehyde, to D-lactic acid. The system is composed of two enzymes, glyoxalase I (Glo-I) and glyoxalase II (Glo-II), and exhibits an absolute requirement for a catalytic quantity of glutathione (GSH). Glo-I catalyzes the isomerization of a hemithioacetal, formed non-enzymatically from methylglyoxal and GSH, to the corresponding a -D-hydroxyacid thioester, s-D-lactoylglutathione (SLG). Glo-II catalyzes the irreversible breakdown of SLG to D-lactate and GSH. We have observed that ATP or GTP significantly inhibits the Glo-II activity of tissue homogenates from various sources. We have developed a rapid, one step chromatography procedure to purify Glo-II such that the purified enzyme remains "sensitive" to inhibition by ATP or GTP (Glo-II-s). Studies indicate that inhibition of Glo-II-s by nucleotides is restricted to ATP, GTP, ADP, and GDP, with ATP appearing most effective. Kinetics studies have shown that ATP acts as a partial non-competitive inhibitor of Glo-II-s activity, and further suggest that two kinetically distinguishable forms of the enzyme exist. The sensitivity of pure Glo-II-s to nucleotide inhibition is slowly lost on storage even at -80° C. This loss is accelerated at higher temperatures or in the presence of ATP. Kinetics studies on the resultant "insensitive" enzyme (Glo-II-i) show that a significant reduction of the affinity of the enzyme for the substrate, SLG, occurs and further suggest that only one form of the enzyme is kinetically distinguishable after "de-sensitization". Tryptophan fluorescence studies of the two enzyme preparations suggest that a subtle conformational change in the enzyme has occurred during de-sensitization. We have also observed that Glo-II-i is "resensitized" to nucleotide inhibition after incubation in the presence of a reagent that reduces disulfide bonds. The resensitized enzyme exhibits an increased KM value similar to that of the original Glo-II-s. Kinetics studies show that ATP or GTP again act as partial non-competitive inhibitors of the resensitized enzyme and suggest that only one form of the enzyme is present. The physiological significance of the two enzyme forms is discussed.
The potential of coelomocyte chemotaxis as an immune biomarker in the earthworm, Lumbricus terrestris
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Coelomocyte migration responses, both random and chemotatic, were examined in the earthworm Lumbricus terrestris. Coelomocyte random migration patterns towards non-stimulatory, non-chemotatic solutions were described. Migration responses to immunostimulatory agents lipopolysaccharides (LPS), N-formly-methionyl-leucyl-phenylalanine (FMLP), sheep erythrocytes, Saccharomyces cerevisiae, Aeromonas hydrophila, Eisenia fetida and Rhabditis pellio were characterized. Chemotaxis was reported to LPS, FMLP, sheep erythrocytes, S. cerivesae and E. fetida. Bio-indicator potential of chemotaxis is discussed relative to variability in migration responses.
Scientific Considerations of Olestra as a Fat Substitute
Olestra is, a sucrose polyester, a noncaloric fat substitute, made from sucrose and several fatty acid esters. It has been approved by the FDA as a food additive used in preparing low-fat deep-frying foods such as savory snacks. Available literature on olestra was evaluated that had both positive and negative connotations. Clinical trials in numerous species of animals including humans were conducted to determine if olestra would affect the utilization and absorption of macro- and micronutrients; the effects of olestra on growth, reproduction, or its toxicity were also examined. The roles of olestra as a fat substitute, how it could effect on humans and the environment, and the potential impacts from its use in large amounts were assessed. Olestra can be removed from the environment by aerobic bacteria and fungi which may be isolated from activated sludge and soils.
Structural analysis of the TOL pDK1 xylGFJQK region and partial characterization of the xylF and xylG gene products
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TOL plasmids encode enzymes responsible for utilization of toluene and related aromatic compounds by Pseudomonas putida, ultimately converting them to central metabolic intermediates. The nucleotide sequence for the 5.6 kb xylGFJQK region of the pDK1 TOL meta operon was determined. DNA sequence analysis revealed the presence of five open reading frames corresponding to xylG (1458 bp), xylF (846 bp), xylJ (783 bp), xylQ (936 bp) and xylK (1047 bp), encoding predicted protein products of 51.6, 31.3, 27.8, 32.8, and 36.6 kDa in size, respectively. The average G+C content of the xylLTEGFJQK region was 65.7%, somewhat higher than the 58.9% seen in the immediately upstream xylXYZ region and substantially more than the 50% G+C content reported for the upper TOL operon of this plasmid. Homology comparisons were made with genes and proteins of related catabolic plasmids. The dmpCDEFG and pWWO xylGFJQK regions exhibit consistently high levels of nucleotide and amino acid homology to pDK1 xylGFJQK throughout the entire region. In contrast, although the nucleotide sequence homology of the Acinetobacter atdCDE region to xylGFJ is high, the homology of atdFG to xylQK is markedly less. Such radical changes in homology between corresponding regions of different operons, combined with variable base and codon usage patterns within and between operons, provides additional support for the idea that the upper and lower operons encoding enzymes of aromatic pathways have evolved independently of one another and that these operons have continued to exchange genetic material with homologous expression units through a series of recombination events. Recombinant plasmids were constructed for individual expression of each of the xylGFJQK genes. HMSD (XylG) and HMSH (XylF) were partially purified and characterized with respect to substrate specificity and kinetic mechanism. Evidence was obtained suggesting that the HMSD reaction occurs via a steady state ordered mechanism or a random mechanism where binding of the first substrate effects the enzyme's affinity for the second substrate.
Syllabus for Advanced Placement Biology
The purpose of this syllabus is to provide a working copy to those teachers of the advanced placement biology course taught at the high school level. Reference materials used were the Texas Education Agency ( TEA ) approved Campbell text Biology and the College Board's, Advanced Placement Biology Laboratory Manual. The syllabus is divided into major topics with outlined notes and includes laboratory exercises as recommended by the College Board. The AP biology course is intended to be equivalent to college biology. College freshman biology courses can differ among colleges and among teachers within the same college. This syllabus is intended to serve as an aid to AP teachers, to cover the topics and experiments as set out by the College Board, and to the high school student, the necessary material to successfully complete the AP examination while providing freshman biology equivalence.
Syllabus Outline for Genetics Lecture and Laboratory
This work is intended to be used as a teaching tool in conjunction with the text cited. It is written in outline format, highlighting the major concepts of each pertinent chapter. In this format, the concepts can be expanded upon at the discretion of the instructor. This work is to be used as a guide for lecture. The basic concepts contained in the outline are in such a format as to be able to work in more information regarding the subject matter if needed. The instructor can work from this outline as a starting point. Major topics in the chapters are highlighted, making lecture notes for the instructor easier to do.