UNT Libraries - 605 Matching Results

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Eutrophication Monitoring and Prediction

Description: Changes in trophic status are often related to increases or decreases in the allocthonous inputs of nutrients from changes in land use and management practices. Lake and reservoir managers are continually faced with the questions of what to monitor, how to monitor it, and how much change is necessary to be considered significant. This study is a compilation of four manuscripts, addressing one of these questions, using data from six reservoirs in Texas.
Date: December 1993
Creator: Cairns, Stefan H., 1949-

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

Regulation, Evolution, and Properties of the ato Qperon and its Gene Products in Escherichia coli

Description: The regulation of short chain fatty acid metabolism has been examined. Metabolism of acetoacetate, and short chain fatty acids such as butyrate and valerate, is predicated upon the expression of genes of the ato operon. Acetoacetate induces expression of a CoA transferase (encoded by the atoDA genes) and expression of a thiolase (encoded by the atoB gene). Metabolism of saturated short chain fatty acids requires the activities of the transferase and thiolase and enzymes of 6-oxidation as well. Spontaneous mutant strains were isolated that were either constitutive or that were inducible by valerate or butyrate instead of acetoacetate.
Date: August 1993
Creator: Chen, Chaw-Yuan

Quantitative Analysis of the Gabaergic System in Cat Primary Somatosensory Cortex and Its Relation to Receptive Field Properties

Description: Sensory neocortex contains a significant number of inhibitory neurons that use gamma-aminobutyric acid (GABA) as their neurotransmitter. Functional roles for these neurons have been identified in physiological studies. For example, in primary somatosensory cortex (SI), blockade of GABAa receptors with bicuculline leads to expansion of receptive fields (RFs). The magnitude of RF enlargement varies between SIpopulations of GABAergic neurons were identified by labeling specific calcium binding proteins.
Date: May 1995
Creator: Li, Jianying

Life History of Mayatrichia ponta Ross (Trichoptera: Hydroptilidae) in Honey Creek, Turner Falls Park, Oklahoma

Description: The life history and ontogenetic microhabitat change of Mayatrichia ponta Ross were investigated in Honey Creek, Turner Falls Park, Murray Co., Oklahoma, U.S.A. from August 1994 to August 1995. The shape of larval cases changed from a small cone to a cylinder. M. ponta had an asynchronous multivoltine life history with considerable cohort and generation overlap; five generations were estimated. The development rate was reduced in winter. The winter generations of M. ponta had wider head capsule widths (136-165 μm) than summer generations (121-145 μm). The sex ratio of adults was 1.43 ♂ : 1 ♀. Fecundity ranged from 46 to 150 eggs/female. Fifth instar larvae and pupae aggregated on the bottom side of substrates. Early instars were distributed evenly on all sides of substrates. General patterns of ontogenetic microhabitat shift in aquatic insects are categorized as flow mediated, flow independent, and population interactions and other resources mediated.
Date: December 1997
Creator: Wang, Yi-Kuang

Construction of a Physical Map of Moraxella (Branhamella) catarrhalis Strain ATCC25238

Description: In order to gain a better understanding of this microorganismand its role in human pathogenesis, a physical map of Moraxella catarrhalis type strain ATCC25238 was constructed using pulsed field gel electrophoresis (PFGE) in combination with Southern hybridization techniques. Restriction endonucleases Not I, Rsr II, and Sma I were used to digest the chromosomal DNA. An overlapping circular map was generated by cross-hybridization of isolated radiolabeled fragments of Moraxella catarrhalis genomic DNA to dried PFGE gels. The number and location of the 16S and 23S ribosomal RNA genes were determined by digestion with l-Ceul enzyme and by Southern hybridization. Virulence-associated genes, the gene for β-lactamase, and housekeeping genes were also placed onto the physical map.
Date: May 1999
Creator: Nguyen, Kim Thuy

Stock and Species Identification of Selected Marine Fishes and Shellfishes Using Allozyme Analysis and Isoelectric Focusing: Implications for Texas Fisheries Management

Description: Allozyme frequencies and general protein patterns were surveyed among selected Texas marine fishes and shellfishes to illustrate the application of biochemical genetic techniques to stock and species identification in fisheries management.
Date: May 1992
Creator: King, Timothy L. (Timothy Lee)

Temporal and Spatial Comparisons of Ambient Toxicity of the Trinity River in Relationship to an Effluent

Description: A toxicological study was initiated because of concerns about allegations that the Texas Water Commission that effluent from the Dallas Central Wastewater Treatment Plant, which discharges into the Trinity River, was affecting downstream water quality. Monthly, flow-weighted composite effluent samples were collected. Grab samples were also collected upstream and downstream from the effluent from April 1989 to August 1991. Toxicity tests were conducted on these samples using Ceriodaphnia dubia as the test organism. Samples were collected four times during this study in which rainfall occurred prior to sampling. In every instance, this "first flush" of the watershed during a rising hydrograph was toxic to C. dubia upstream. Analyzing toxicity by season resulted in a statistically significantly lower neonate production in the effluent than in the river samples during the months of June, July, and August. This impact on neonate production was suspected of being caused by organic pesticides which are used for insect control on lawns. The effluent was never acutely toxic to C. dubia. Primarily, toxic occurrences in either the effluent or the river samples were primarily of a chronic nature. Overall, survival of C. dubia was affected more frequently at the upstream site than in the effluent or the downstream site. Because EPA's Phase I Acute Toxicity Identification Evaluations (TIEs) methods were designed for identifying acute toxicity, two alternative strategies were attempted to identify chronic toxicity. The first attempt was the modification of the phase I acute TIE methodologies. This was done by processing more sample through the phase I characterization tests. This approach was inadequate due to toxicity that occurred during the last several days of the seven-day C. dubia reproduction test. The second strategy for identifying chronic toxicity within a TIE involved the use of freeze concentration. During this preliminary investigation ofthe efficiency of freeze concentration, ...
Date: December 1993
Creator: Hall, David B., 1958-

Nesting Ecology of the Dickcissel (Spiza americana) on a Tallgrass Prairie Relict in North Central Texas

Description: Eighty-three species of vascular plants were inventoried on the prairie relict during peak dickcissel nesting. Based on foliar cover and occurrence frequency, the five dominant plants were heath aster (Aster ericoides), eastern gammagrass (Tripsacum dactyloides), little bluestem (Schizachyrium scoparium), sensitive briar (Schrankia roemeriana) and meadow dropseed (Sporobolus asper). Sixty-one percent of dickcissel nests were constructed on or immediately next to three plant species: eastern gammagrass, sensitive briar and green milkweed.
Date: May 1993
Creator: Steigman, Kenneth Lee

Isolation and Characterization of the Operon Containing Aspartate Transcarbamoylase and Dihydroorotase from Pseudomonas aeruginosa

Description: The Pseudomonas aeruginosa ATCase was cloned and sequenced to determine the correct size, subunit composition and architecture of this pivotal enzyme in pyrimidine biosynthesis. During the course of this work, it was determined that the ATCase of Pseudomonas was not 360,000 Da but rather present in a complex of 484,000 Da consisting of two different polypeptides (36,000 Da and 44,000 Da) with an architecture similar to that of E. coli ATCase, 2(C3):3(r2). However, there was no regulatory polypeptide found in the Pseudomonas ATCase.
Date: May 1993
Creator: Vickrey, John F. (John Fredrick), 1959-

Interactions between Carotid and Cardiopulmonary Baroreceptor Populations during Dynamic Exercise in Man

Description: During dynamic exercise the arterial baroreflexes have been thought to reset to the prevailing level of systemic pressure in order to modulate transient changes in blood pressure with the same sensitivity (gain) as at rest. To test this hypothesis, cardiovascular responses to dynamic exercise and carotid baroreflex responses to graded neck suction and neck pressure (NS/NP) were examined in seven men of moderate fitness (V02 = 41.4±3.6 ml O2*kg^-1*min^-1) during two levels (20% and 40% of peak oxygen uptake) of steady-state exercise. In addition, deactivation of cardiopulmonary baroreceptors has been thought to increase carotid baroreflex responsiveness in the quiescent state in man.
Date: May 1993
Creator: Potts, Jeffrey Thomas

Subcloning and Nucleotide Sequence of Two Positive Acting Regulatory Genes, xy1R and xy1S, from the Pseudomonas putida HS1 TOL Plasmid PDK1

Description: TOL plasmids of Pseudomonas putida encode enzymes for the degradation of toluene and related aromatics. These genes are organized into two operons regulated by the Xy1R and Xy1S transcriptional activators. Previous analysis of the TOL pDK1 catechol-2,3-dioxygenase gene (xy1E) and a comparison of this gene to xy1E from the related TOL plasmid pWW0, revealed the existance of a substantial level of sequence homology (82%).
Date: May 1992
Creator: Chang, Teh-Tsai

Characterization of Aspartate Transcarbamoylase and Dihydroorotase in Moraxella Catarrhalis

Description: Bacterial aspartate transcarbamoylases (ATCase's) are divided into three classes that correspond to taxonomic relationships within the bacteria. The opportunistic pathogen Moraxeila catarrhalis has undergone several reclassifications based on traditional microbiological criteria. The previously uncharacterized ATCase from M. catarrhalis was purified to homogeneity and its chemical properties characterized. The ATCase from M. catarrhalis is a class C ATCase with an apparent molecular mass of 480-520 kDa. The M. catarrhalis ATCase is a dodecomer composed of six 35 kDa polypeptides and six 45 kDa polypeptides. The enzyme has an unusually high pH optimum of greater than pH 10. The enzyme exhibited hyperbolic kinetic with a Km for aspartate of 2 mM. A single, separate 78 kDa dihydroorotase from M. catarrhalis was identified and it was not associated with ATCase. These data support the reclassification of M. catarrhalis out of the Neisseriaceae family.
Date: May 1998
Creator: Fowler, Michael A. (Michael Allen), 1961-

Assessing Effects of an Environmental Education Field Science Program Fostering Responsibility at an Urban Middle School

Description: The study investigated the ability of an extracurricular program to influence environmental responsibility of sixth and seventh graders. The Children's Environmental Attitude and Knowledge Survey (CHEAKS) was evaluated for appropriateness in assessing the worth of this particular environmental education strategy emphasizing water quality fieldwork and technology. CHEAKS is designed with psychometric reliability and validity that may be used in comparing disparate programs. Wilcoxon two sample tests were used to analyze data gathered from two student groups; one participated in an "Enviro-Mentals Club"; the other received no treatment. Analysis showed no significant change in environmental attitudes between groups, but did show significance (p <= 0.05) in environmental knowledge growth. Therefore, the investigated program had marginal success in influencing environmental responsibility.
Date: May 1999
Creator: Sills, Blake

Nutrient Effects on Autofragmentation of Myriophyllum Spicatum L.

Description: A 2 x 2 factorial design investigated effects of sediment nitrogen and water potassium levels on autofragment production. Reduced nitrogen levels significantly increased autofragment production whereas potassium levels did not significantly alter production. Up to 50% of autofragment production abscised from parent plants grown under low nitrogen conditions compared to 12% or less under high nitrogen conditions.
Date: August 1998
Creator: Smith, Dian H. (Dian Helen)

Identification and Characterization of the Pyrimidine Biosynthetic Operon in Streptomyces griseus

Description: To further understand the ATCase/DHOase bifunctional complex formed in Streptomyces, the genes encoding these and other pyrimidine enzymes were identified and characterized. Polymerase chain reaction (PCR) was utilized in this effort. Primers were constructed by selecting conserved regions of pyrimidine genes from known gene and protein sequences of a wide variety of organisms. These sequences were then optimized to Streptomyces codon usage. PCR products were obtained from internal sites within pyrimidine genes and also from primer combinations of different genes. The size, orientation, and partial sequence of the resulting products shows that Streptomyces has a gene organization of pyrR followed by pyrB, pyrC, carA, carB, and pyrF in an operon similar to that found in other Gram-positive bacteria.
Date: May 1998
Creator: Hooten, Jody J. (Jody Jeran)

Contemporary Biology Curriculum for Non-majors

Description: The proposed biology curriculum for non-majors has one main objective, namely to improve scientific literacy among college students. The National Science Education Standards defines scientific literacy as "the knowledge and understanding of scientific concepts and processes required for personal decision making, participation in civic and cultural affairs, and economic productivity". The suggested strategies to accomplish this goal are to limit the number of topics covered, introduce relevant scientific terminology, emphasize general biological concepts and themes, and hone critical thinking and problem-solving skills. Activities such as group projects, written and oral assignments, and class discussions are effective tools to assess student ability to communicate scientifically. It is also important for students to make connections between the course subject matter and how it affects real life events.
Date: August 1998
Creator: Smallwood, Susan

Molecular and Kinetic Characterization of the Aspartate Transcarbamoylase Dihydroorotase Complex in Pseudomonas putida

Description: Aerobic Gram negative bacteria such as Pseudomonas putida were reported to possess class A ATCases and to have a M.W. of 360 kD. The nucleotide sequence of the P. putida pyrBC was determined to answer this question once and for all. The expected regulatory gene was not found. It is shown that the P. putida pyrB gene is overlapped by pyrC by 4 bp. The P.putida pyrB is 1005 bp (335 aa) in length and the pyrC is 1275 bp (425 aa) long. Both of these genes complement E. coli mutants with their respective genotypes. Another finding borne out from the sequence is an effector binding site at the N-terminus of pyrB of P. putIda. The binding site shows that effectors compete with carbamoylphosphate for the active site. In this dissertation, it is shown that the ATCase of P.putida is a trimer of M.W. of 109 kD (3 x 36.4 kD) and that the gene encoding pyrB is overlapped by the pyrC gene which encodes DHOase. It is also shown that the pyrBC encoded enzymes copurify as a dodecameric complex with a M.W. of 484 kD.
Date: May 1992
Creator: Schurr, Michael J. (Michael John)

Evaluation of Sequential Events in Phagocytosis by Earthworm Coelomocytes as Potential Immunotoxicity Biomarkers

Description: This research evaluated the potential of activation and attachment, as sequential companion biomarkers of phagocytosis by earthworm, Lumbricus terrestris, immunoactive coelomocytes for use in immunotoxicology. The potential was assessed by exposing earthworms to sublethal concentrations of CuSO4 and Arochlor 1254®, chemicals used as reference or standard immunotoxicants.
Date: August 1998
Creator: Murray, Stephanie Mae

Conception and Design of Constructed Wetland Systems to Treat Wastewater at the Biosphere 2 Center with Use of Reaction Rate Models and the Habitat Evaluation Procedure to Determine the Effects of Designing for Wildlife Habitat on Treatment Efficiency

Description: A study was undertaken to explore relationships between wetland characteristics which make them efficient water purifiers versus their ability to serve as wildlife habitat. The effects of designing constructed wetlands for improved habitat on water treatment efficiencies were quantified. Results indicate that some sacrifice in treatment efficiency is required and that the degree of efficiency reduction is dependant upon pollutant loading rates. However, sacrifice in efficiency is much smaller than increase in habitat quality, and can be offset by increasing wetland area. A practical, theoretical application was then attempted.
Date: May 1998
Creator: Clingenpeel, Glenn C. (Glenn Christopher)

Responses of Cultured Neuronal Networks to the Cannabinoid Mimetic Anandamide

Description: The effects of cannabinoid agonists on spontaneous neuronal network activity were characterized in murine spinal cord and auditory cortical cultures with multichannel extracellular recording using photoetched electrode arrays. Different cultures responded reproducibly with global decreases of spiking and bursting to anandamide and methanandamide, but each agonist showed unique minor effects on network activity. The two tissues responded in a tissue-specific manner. Spontaneous activity in spinal tissue was terminated by 1 μM anandamide and 6.1 μM methanandamide. Cortical activity ceased at 3.5 μM and 2.8 μM respectively. Irreversible cessation of activity was observed beyond 8 μM for both tissues and test substances. Palmitoylethanolamide, demonstrated that CB2 receptors were not present or not responsive. However, the data strongly suggested the presence of CB1 receptors.
Date: May 1998
Creator: Morefield, Samantha I. (Samantha Irene)

Use of tRNA Gene Probes to Identify Polymorphic Loci in the Bovine Genome

Description: A 30-mer oligonucleotide probe encoding the "A box" and anticodon loop regions of a human glycine tRNA gene was used to isolate a 581bp DNA fragment from a bovine genomic DNA library. Although the cross-hybridizing segment of DNA was found not to encode any tRNA gene or pseudogene, a region with homology to the "C-element" of the "BOV-tA" type Alulike artiodactyl retroposons was identified. This cross-hybridization was determined to be the result of conserved RNA polymerase III promoter elements in the probe portion of the tRNA gene and these repetitive elements. A microsatellite repeat (TC) was also found associated with this element. Future screening for bovine tRNA genes will require the use of a) longer probes and higher stringency hybridization conditions or b) the simultaneous screening with probes from the 5' and 3' ends of the gene which avoid the conserved Pol III promoter boxes.
Date: August 1998
Creator: Shariat, Parvaneh

Medial Medulla Networks in Culture: a Multichannel Electrophysiologic and Pharmacological Study

Description: Spontaneously active primary cultures obtained from dissociated embryonic medial medulla tissue were grown on microelectrode arrays for investigating burst patterns and pharmacological responses of respiratory-related neurons. Multichannel burst rates and spike production were used as primary variables for analysis. Pacemaker-like neurons were identified by continued spiking under low Ca++/high Mg++conditions. The number of pacemakers increased with time under synaptic blocking medium. Sensitivity to CO2 levels was found in some neurons. Acetylcholine changed activity in a complex fashion. Curare, atropine and gallamine modified ACh effects. Eserine alone was ineffective, but potentiated ACh-induced responses. Norepinephrine caused channel-specific increases or decreases, whereas dopamine and serotonin had little effect at 30 μM. GABA and glycine stopped most spiking at 70 μM. Developmental changes in glycine sensitivity (increasing with age) were also observed. It is concluded that pacemaker and chemosensitive neurons develop in medial medulla cultures, and that these cultures are pharmacologically histiotypic.
Date: August 1998
Creator: Keefer, Edward W. (Edward Wesley)

Phagocytosis by Earthworm Coelomocytes : A Biomarker for Immunotoxicity of Hazardous Waste Site Soils

Description: Several biomarkers (cell viability and phagocytosis) based on earthworm (Lumbricus terrestris) immune cells (coelomocytes), together with whole-worm mortality (LC/LD50's), were used to assess a bioremediation attempt to reduce pentachlorophenol (PCP) toxicity in a former wood processing hazardous waste site (HWS).
Date: December 1997
Creator: Giggleman, Marina A.