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  Partner: UNT Libraries
 Decade: 2000-2009
 Year: 2001
 Degree Discipline: Biology
 Collection: UNT Theses and Dissertations
Age-Dependent Effects Of Chronic GABAA  Receptor Blockade In Barrel Cortex

Age-Dependent Effects Of Chronic GABAA Receptor Blockade In Barrel Cortex

Date: May 2001
Creator: Gargan, Lynn
Description: GABAA receptor binding is transiently increased in rat whisker barrels during the second postnatal week, at a time when neurons in the developing rat cortex are vulnerable to excitotoxic effects. To test whether these GABAA receptors might serve to protect neurons from excessive excitatory input, polymer implants containing the GABAA receptor antagonist bicuculline were placed over barrel cortex for a 4-day period in young (postnatal days 8 - 12) and adult rats. In the cortex of young, but not adult rats, the chronic blockade of GABAA receptors resulted in substantial tissue loss and neuron loss. The greater loss of neurons in young rats supports the hypothesis that a high density of GABAA receptors protects neurons from excessive excitatory input during a sensitive period in development.
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Comparative Morphology of Sensilla Styloconica on the Proboscis of North American Nymphalidae and Other Selected Taxa: Systematic and Ecological Considerations.

Comparative Morphology of Sensilla Styloconica on the Proboscis of North American Nymphalidae and Other Selected Taxa: Systematic and Ecological Considerations.

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Date: December 2001
Creator: Petr, Daniel
Description: Sensilla styloconica on the proboscis of 107 species of North American and tropical butterflies were comparatively studied using the scanning electron microscope. Focus was on 76 species of North American Nymphalidae representing 45 genera and 11 subfamilies. Nomenclature for generalized and specific types of nymphalid sensilla is proposed. Written descriptions and micrographs are presented for each species studied. Morphological features were generally consistent for all or most species within genera and sometimes within subfamilies, with specified exceptions. Statistical analysis revealed significant differences for six of eight variables tested between two distinct feeding guilds of North American Nymphalidae. Average number, density, extent of proboscis coverage with sensilla, their total length, and shoulder spine length were all significantly greater in the non-nectar feeding guild than in nectar feeders, and may indicate adaptation for greater efficiency in feeding on flat surfaces. The greater frequency of apical shoulder spines in non-nectar feeders may represent adaptation for protection of sensory pegs from mechanical abrasion during feeding, or for anchoring the flexible proboscis tip to the surface. Correlation analysis revealed 9 out of 28 positive correlations in nectar feeders and 5 out of 28 in non-nectar feeders. Results of preliminary cladistic analysis were not considered to ...
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The Developmental Physiology of the Zebrafish: Influence of Environment and Cardiovascular Attributes

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

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Date: August 2001
Creator: Bagatto, Brian
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 ...
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Investigations of neuronal network responses to electrical stimulation in murine spinal cultures.

Investigations of neuronal network responses to electrical stimulation in murine spinal cultures.

Date: December 2001
Creator: Sparks, Christopher A.
Description: Spontaneous activity in neuronal networks in vitro is common and has been well documented. However, alteration of spontaneous activity in such networks via conditioning electrical stimulation has received much less experimental attention. Two different patterns of electrical stimulation were used to enhance or depress the level of spontaneous activity in spinal cord cultures. High-frequency stimulation (HFS), a method routinely shown to increase the efficacy of synaptic transmission, was employed to augment spontaneous activity. Low-frequency stimulation (LFS), the technique often applied to depress synaptic efficacy, was employed to decrease spontaneous activity. In addition, LFS was used to reverse the effect of HFS on spontaneous activity. Likewise, HFS was applied to counter the effect of LFS. Because these networks were grown on multi-microelectrode plates (MMEPs), this allowed the simultaneous stimulation of any combination of the 64 electrodes in the array. Thus, the possible differences in response to single versus multi-electrode stimulation were also addressed. Finally, test-pulses were delivered before and after the conditioning stimulation on the same stimulation electrode(s) in order to assess the change in mean evoked action potentials (MEAPs). Dissociated spinal tissue from embryonic mice was allowed to mature into self-organized networks that exhibited spontaneous bursting activity after two weeks ...
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A laboratory course in experimental genetics for the biology major.

A laboratory course in experimental genetics for the biology major.

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Date: December 2001
Creator: Lux, Melissa McNeil
Description: This manual has been designed for a class of twenty- four students concurrently enrolled in the lecture course. The laboratory aids in the learning process and fosters an interest in the science of genetics. This manual and the experiments contained within are both informative and fun. The manual correlates with and expands upon the genetics course. Each investigation, with the exception of the Drosophila melanogaster project, can be completed in a 3-4 hour timeframe. This manual provides a “hands on” experience of theories simply discussed in the lecture course. This manual is intended to be a one-source manual where each investigation is designed to include an adequate introduction. Special attention has been given for each investigation with both the student and instructor in mind.
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Life History and Secondary Production of Caenis latipennis Banks (Ephemeroptera: Caenidae) in Honey Creek, Oklahoma

Life History and Secondary Production of Caenis latipennis Banks (Ephemeroptera: Caenidae) in Honey Creek, Oklahoma

Date: August 2001
Creator: Taylor, Jason M.
Description: A study of the life history and secondary production of Caenis latipennis, a caenid mayfly, was conducted on Honey Creek, OK. from August 1999 through September 2000. The first instar nymph was described. Nymphs were separated into five development classes. Laboratory egg and nymph development rates, emergence, fecundity, voltinism, and secondary production were analyzed. C. latipennis eggs and nymphs take 132 and 1709 degree days to develop. C. latipennis had an extended emergence with five peaks. Females emerged, molted, mated, and oviposited in an estimated 37 minutes. Mean fecundity was 888.4 ± 291.9 eggs per individual (range 239 -1576). C. latipennis exhibited a multivoltine life cycle with four overlapping generations. Secondary production was 6,052.57 mg/m2/yr.
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A Novel Phytoestrogen that Acts as an Agonist for Human Estrogen Receptors.

A Novel Phytoestrogen that Acts as an Agonist for Human Estrogen Receptors.

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Date: December 2001
Creator: Pearce, Virginia
Description: Estrogen is the natural agonist of the estrogen receptor (ER). However, certain plant-derived compounds or phytoestrogens have been identified that mimic estrogens and act as agonists and/or antagonists of ERs, depending on subtype and target tissue. Understanding how phytoestrogens interact with ERs, and therefore effect the estrogenic response, may prove beneficial in hormone replacement therapy and in the prevention and treatment of hormone-related diseases. Using Thin Layer Chromatography, gas chromatography/mass spectrometry (GC/MS), and proton nuclear nagnetic resonance (HNMR), I identified 4-ethoxymethylphenol (4EM) found in Maclura pomifera. While most phytoestrogens are heterocyclic compounds, 4EM is a simple phenol that acts as an agonist of ER-alpha and -beta in HeLa and MCF-7 cells. To study the effect of 4EM on ER-alpha and -beta activity, I performed transient transfection assays and showed that 4EM activates ER dependent gene transcription in a dose dependent manner in both ER subtypes. Further, 4EM- mediated transcription in ER-alpha, like estrogen, was enhance in the presense of co-activators, SRC-1 (steroid receptor coactivator-1), CBP (CREB binding proteins), and E6-AP (E6-associated protein) and inhibited by trans-4- hydroxytamoxifen (4HT). I found that 4EM was specific for ER and did not activate transcription of the progesterone receptor in HeLa cells.
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A Study of the Pyrimidine Biosynthesis Pathway and its Regulation in Two Distinct Organisms:  Methanococcus jannaschii and Pseudomonas aeruginosa

A Study of the Pyrimidine Biosynthesis Pathway and its Regulation in Two Distinct Organisms: Methanococcus jannaschii and Pseudomonas aeruginosa

Date: December 2001
Creator: Patel, Seema R.
Description: Methanococcus jannaschii is a thermophilic methane producing archaebacterium. In this organism genes encoding the aspartate transcarbamoylase (ATCase) catalytic (PyrB) and regulatory (PyrI) polypeptides were found. Unlike Escherichia coli where the above genes are expressed from a biscistronic operon the two genes in M. jannaschii are separated by 200-kb stretch of genome. Previous researchers have not been able to show regulation of the M. jannaschii enzyme by the nucleotide effectors ATP, CTP and UTP. In this research project we have genetically manipulated the M. jannaschii pyrI gene and have been able to assemble a 310 kDa E. coli like enzyme. By using the second methionine in the sequence we have shown that the enzyme from this organism can assemble into a 310 kDa enzyme and that this enzyme is activated by ATP, CTP and inhibited by UTP. Thus strongly suggesting that the second methionine is the real start of the gene. The regulation of the biosynthetic pathway in Pseudomoans aeruginosa has previously been impossible to study due to the lack of CTP synthase (pyrG) mutants. By incorporating a functional uridine (cytidine) kinase gene from E. coli it has been possible to isolate a pyrG mutant. In this novel mutant we have ...
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Submerged wood inhabiting macoinvertebrates of the Elm Fork of the Trinity River, Texas: Assemblage analyses, comparisons to the benthic fauna, and a study of  Cyrnellus fraternus (Trichoptera: Polycentropodidae)

Submerged wood inhabiting macoinvertebrates of the Elm Fork of the Trinity River, Texas: Assemblage analyses, comparisons to the benthic fauna, and a study of Cyrnellus fraternus (Trichoptera: Polycentropodidae)

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Date: August 2001
Creator: Johnson, Zane B.
Description: Taxonomic composition and spatio-temporal variability of macroinvertebrates inhabiting snags were examined from an 8-km segment of the Elm Fork of the Trinity River. Seventy-seven macroinvertebrate taxa were collected from submerged wood during the study. Assemblages were highly variable spatially and temporally, especially among seasons. An ordination of species and environment did not find snag taxa to have striking correlations with many of the selected environmental variables, although there were some trends in flow-mediated species distributions. There were significant seasonal differences in the abundances of some taxa, particularly among the Chironomidae (Diptera). The Tribe Orthocladiini was numerically abundant during the winter, while the Tribes Chironomini and Tanytarsini dominated the summer and autumn. Additionally, this study included a secondary production and microdistribution analysis of a population of the caddisfly Cyrnellus fraternus. Distributions of C. fraternus were restricted to snags, the most stable substratum for retreat building and for resisting periodic high waters. Larvae were not found in the soft sand and mud benthic habitats near submerged wood. The insects were multivoltine with a minimum of three generations per year. Pupae were collected July through September and adults emerged from May through October. The population overwintered as larvae. Estimated annual production was 1,015.4 ...
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Unique applications of cultured neuronal networks in pharmacology, toxicology, and basic neuroscience

Unique applications of cultured neuronal networks in pharmacology, toxicology, and basic neuroscience

Date: May 2001
Creator: Keefer, Edward W.
Description: This dissertation research explored the capabilities of neuronal networks grown on substrate integrated microelectrode arrays in vitro with emphasis on utilizing such preparations in three specific application domains: pharmacology and drug development, biosensors and neurotoxicology, and the study of burst and synaptic mechanisms. Chapter 1 details the testing of seven novel AChE inhibitors, demonstrating that neuronal networks rapidly detect small molecular differences in closely related compounds, and reveal information about their probable physiological effects that are not attainable through biochemical characterization alone. Chapter 2 shows how neuronal networks may be used to classify and characterize an unknown compound. The compound, trimethylol propane phosphate (TMPP) elicited changes in network activity that resembled those induced by bicuculline, a known epileptogenic. Further work determined that TMPP produces its effects on network activity through a competitive inhibition of the GABAA receptor. This demonstrates that neuronal networks can provide rapid, reliable warning of the presence of toxic substances, and from the manner in which the spontaneous activity changes provide information on the class of compound present and its potential physiological effects. Additional simple pharmacological tests can provide valuable information on primary mechanisms involved in the altered neuronal network responses. Chapter 3 explores the effects produced ...
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