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Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas
Pharmaceuticals have routinely been detected in the environment resulting in a growing concern about whether these drugs could elicit effects on aquatic organisms. The concerns are centered on the highly conserved nature of mammalian therapeutic targets in fish. These pharmaceuticals are found at very low levels in the environment, which can result in sub-lethal effects in aquatic organisms. Therefore, 28 d early-life stage studies were conducted on six pharmaceuticals to assess their impacts on survival and growth fathead minnow larvae. Two pharmaceuticals tested, carbamazepine and fenofibrate, resulted in no alterations to survival and growth. However, amiodarone, clozapine, dexamethasone, and levonorgestrel (LNG) reduced survival at concentrations tested with LNG being the most potent at 462 ng/L. Survival was increased with amiodarone and clozapine; however LNG significantly decreased growth at 86 ng/L. Therefore, the most potent pharmaceutical tested was the synthetic progestin LNG with survival and growth impacts at concentrations less than 1 μg/L. Further analysis was conducted by measuring specific endocrine related mRNA transcript profiles in FHM larvae following the 28 d ELS exposure to LNG. Transcripts of 3β-HSD, 20β-HSD, and FSH were significantly down-regulated following 28 d exposure to both 16.3 and 86.9 ng/L LNG. Also, CYP19a expression was significantly down-regulated at 86.9 and 2392 ng/L LNG. Subsequently, a second study examined time periods that may be most sensitive (e.g., windows of sensitivity) for FHM larvae exposed to LNG. Larvae were exposed to a single concentration of LNG (i.e. LOECgrowth of 86.2 ng/L as determined in the 28 d ELS study) for different time periods starting with fertilized egg through 28 dph. Growth and mRNA expression of the four differentially expressed transcripts from the first study were measured. Regardless of the duration of exposure, LNG significantly decreased growth in fathead minnow larvae at day 28. For both 20β-HSD and CYP19a, mRNA expression was decreased following exposure to LNG; however, these transcripts returned to baseline levels after removal of LNG. 3β-HSD and FSH showed similar trends after exposure to LNG with 7-14 d and 14-28 d exposures exhibiting a decrease in expression; however, FSH expression returned to baseline once removed for LNG exposure. Based on these data, 3β-HSD was the only transcript to remain down regulated after LNG exposure. Together these data suggest LNG can negatively impact FHM larval survival and growth, with significant alterations in endocrine related responses. However, these changes in endocrine related responses may not directly correlate to the changes in growth demonstrated with LNG exposure to fathead minnows. Therefore, additional research is warranted to ascertain additional mechanisms, either endocrine related or non-endocrine functions, related to changes in growth of larval fathead minnows.
Analysis of Phytoplankton Responses to Water Chemistry Dynamics in a Moderately Eutrophic North Texas Reservoir
Canonical correspondence analysis (CCA) was used to explore relationships between measured environmental variables and in situ phytoplankton communities in a moderately eutrophic North Texas Reservoir.
Evaluation of a Constructed Wetland to Reduce Toxicity from Diazinon at the Pecan Creek Wastewater Treatment Plant, Denton, TX
The City of Denton Pecan Creek Wastewater Treatment Facility has periodically failed effluent toxicity testing. A Toxicity Identification Evaluation has determined that Diazinon in the effluent is contributing to the observed toxicity. Chlorpyrifos is also implicated as a factor. The City of Denton constructed a half acre experimental wetland to remove Diazinon related toxicity. Results from spiking and microcosm experiments indicate that the wetland can reduce the Diazinon.
Effects of External Electric Fields on Light Transmittance in Isolated Crayfish Nerves
Acute effects of a pulsed external electric field (PEEF) at 20 V/cm and a d.c. EEF at 90 V/cm on light transmittance in an isolated compound crayfish nerve was measured. In a third series, the nerve was pre-treated with the Na+ channel blocker tetrodotoxin (TTX). A PEEF produced an irreversible increase in the variation of light transmittance in normal nerves but a reversible increase in TTX treated nerves. This data was statistically insignificant. The d.c. EEFs produced a reversible and statistically significant enhancement of variation in light transmittance in both untreated and TTX-treated nerves. The findings may be due to either (1) an alteration in the ion/fluid flux within the nerve or (2) a physical alteration of protein molecules in the membranes.
Nucleotide Sequence of a Bovine Arginine Transfer RNA Gene
A single plaque-pure lambda clone designated λBA84 that hybridized to a ˆ32P-labeled bovine arginine tRNA was isolated from a bovine genomic library harbored in a lambda bacteriophage vector. A 2.3-kilobase segment of this clone was found to contain an arginine transfer RNAccg gene by Southern blot hybridization analysis and dideoxyribonucleotide DNA sequencing. This gene contains the characteristic RNA polymerase III split promoter sequence found in all eukaryotic tRNAs and a potential RNA polymerase III termination site, consisting of four consecutive thymine residues, in the 3'-flanking region. Several possible cis-acting promoter elements were found within the 5'-flanking region of the sequenced gene. The function of these elements, if any, is unknown.
The Role of Gabergic Inhibition in Modulating Receptive Field Size of Cuneate Neurons
A blockade of GABAergic inhibition increases the receptive field(RF) size of most somatosensory cortex (SI) and some ventrobasal thalamus (VB) neurons. The results suggest RF size of cuneate neurons may be modulated through GABAa and GABAb receptors, independent of firing frequency.
Heat Shock Proteins in Ascaris suum
Ascaris suum were exposed to a number of stressors, including heavy metals and both high (40°C) and low (18°C) temperatures. The 70kD and 90kD heat shock proteins (HSPs) in the different A. suum tissues were analyzed by Western blot and quantitated by Macintosh Image Program.
Upper and Lower Temperature Tolerances of Three Freshwater Game-Fish Species Exposed to Cycling Temperatures
A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.
Attenuation of Escherichia Coli Aspartate Transcarbamoylase Expressed in Pseudomonas Aeruginosa Mutant and Wild Type Strains
No apparent repression of pyr gene expression in Pseudomonas aeruginosa is observed upon addition of exogenous pyrimidines to the growth medium. Upon introduction of the subcloned Escherichia coli pyrBI genes for aspartate transcarbamoylase (ATCase) into a P. aeruginosa pyrB mutant strain, repression was observed in response to exogenously fed pyrimidine compounds. The results proved that it is possible to bring about changes in pyrimidine nucleotide pool levels and changes in transcriptional regulation of gene expression as a result. Thus, the lack of regulatory control in P. aeruginosa pyr gene expression is not due to an inability to take up and incorporate pyrimidine compounds into metabolic pools, or to an inability of the RNA polymerase to respond to regulatory sequences in the DNA but is probably due to a lack of specific regulatory signals in the promoter of the genes themselves.
A Two Semester Life Science Syllabus for Use in Texas Public Schools with Seventh Grade Students
The problem of using a state adopted textbook written to apply to a large body of students with varying interests and needs was overcome by using a detailed syllabus that arranged course content in a meaningful sequence that appealed to student interest. The outlined syllabus prepared a two semester life science curriculum to be used by the teacher to guide lesson planning. Both semesters were divided into three units each. Materials included in the syllabus were given to actual student groups in real classroom settings. Since hands on learning was an important part of classroom instruction, two laboratory sections were included in the appendices to be used with the syllabus.
The Removal of Linseed Oil Vapors by Biodegradation
Linseed oil is very important in industry but its use is limited due to noxious vapors produced by oxidation on exposure to air. Since some of the products are toxic, release of linseed oil vapors to the environment is normally prohibited. In order to remove the odorous compounds, a biofilter system based on bacterial metabolism was designed and the major premises of bioremediation were studied. A total of five bacterial strains capable of using linseed oil vapors as their sources of carbon and energy were isolated from soil. The individual organisms were also mixed to form a bacterial consortium. The mixed population was able to degrade linseed oil vapors with more than 99 per cent efficiency. According to this research, a successful biodegradation system was designed and, theoretically, this system could be applied to the removal of linseed oil vapors in any industrial plant air stream.
GABAᴀ Receptors in Rat Whisker Barrel Cortex: Effects of Sensory Deprivation
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.
Nicotinic Acetylcholine Receptor α3 mRNA in Rat Visual System After Monocular Deprivation
In situ hybridization was used to examine effects of monocular enucleation on nicotinic acetylcholine receptor subunit cc3 mRNA in the rat dLGNand visual cortex. After 28 days postoperative, there were no significant differences in α3 mRNA density between the contralateral (deprived) and ipsilateral (non-deprived) sides. The lack of obvious effects of visual deprivation on α3 mRNA density suggests that other factors, possibly intrinsic to dLGNand visual cortex, govern the postnatal expression of α3 mRNA.
The Influence of a Return of Native Grasslands upon the Ecology and Distribution of Small Rodents in Big Bend National Park
In the southwestern United States there is a delicate balance between the existing grasslands and the rodent fauna. The purpose of this investigation was to determine the influence of secondary succession of native grasslands upon the ecology and distribution of small rodents. Two methods of determining the rodent species were plot quadrates and trap lines using Sherman live traps.
Passive Dispersal of Algae and Protozoa Internally and Externally by Selected Aquatic Insects
This investigation was concerned with three aspects of the problem of passive dispersal of algae and protozoa by aquatic insects: the role of odonates in passive dispersal of viable small aquatic organisms, the passage of viable algae and protozoa through digestive tracts of field-collected herbivorous and carnivorous aquatic insects, and the viability duration of selected algae, during insect transport under monitored conditions.
Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela
Light spectra distributions were measured in two different montane forests: temperate and tropical. Spectral light measurements were made in different sized canopy gaps in the conifer forest at H. J. Andrews Experimental Forest in Oregon, USA. Researchers at Oregon State University created these gaps of 20 m, 30 m, and 50 m in diameter. In the tropical cloud forest, spectral light measurements were made in two plots that were permanently established at La Mucuy Parque Nacional in Venezuela, in collaboration with researchers at Universidad de Los Andes. In both studies, spectra and distributions of physiologically active light were analyzed: red, far-red, R/FR ratio, and blue light.
Callibaetis Floridanus (Ephemeroptera: Baetidae) Life History and Production in a West Texas Playa
A life history study of Callibaetis floridanus was conducted over the wet cycle of a playa on the Southern High Plains of Texas from June through September 1995.
The Effects of Organic Surface Amendments on Soil Nutrients and Initial Tree Establishment
This study examined the effects of replicating woodland soil surface horizonation on the nutrient status of underlying soils and the initial establishment and growth of trees. A total of 283 container grown trees were planted in a bufferzone around a future landfill site. Control amendments consisted of an 8 cm layer (0.5 m3) of wood chips applied in a circular area of 4.6 m2 around the trees' planting pit. For the treatment, a 2.5 cm layer of composted biosolids (0.15 m3 or 80 Mg/ha) was applied in a circular area of 4.6 m2 around the trees' planting pit followed by an 8 cm layer (0.5 m3) of wood chips. The results indicate that the replication of woodland soil surface attributes using composted biosolids can significantly improve the nutrient status of underlying soil. Some significant effects were seen under control conditions, too. However, the effects on tree establishment and growth parameters were, for the most part, not statistically significant.
The Use of Similarity Indicies to Assess the Spatial Differences of the Phytoplankton Communities in Lake Ray Roberts, Texas
A study of the phytoplankton communities of Lake Ray Roberts was conducted at three sampling sites on two sampling dates during the summer of 1995, assessing both community structure and chlorophyll a concentrations. Eight similarity indices were then used to characterize and compare the communities of these sites. Both community similarity and chlorophyll a concentrations were evaluated using a minimum detectable difference equation to determine the amount of change that must occur in these parameters in order to be deemed statistically significant. The Bray-Curtis Index was shown to be the most adequate index evaluated, and was subsequently used in conjunction with bootstrap analysis to determine the similarity between the three sampling sites.
Evaluating Fish Impingement and Entrainment at the Comanche Peak Steam Electric Station
This study was designed to determine if impingement and entrainment by cooling water intake at the Comanche Peak Steam Electric Station have an adverse impact upon the Squaw Creek Reservoir fish population. The yearly impingement of fish was estimated to be 262,994 of 14 species. The threadfin shad (Dorosoma petenense) accounted for 96% of this total. Entrainment of eggs and larvae for a five month period was estimated to be 15,989,987 and 42,448,794 respectively. Two fish population studies were performed on Squaw Creek Reservoir to help assess impact. It was determined that the losses due to impingement and entrainment have no adverse impact upon the fish population of Squaw Creek Reservoir.
Descriptions, Life History and Case-Building Behavior of Culoptila cantha (Trichoptera: Glossosomatidae) in the Brazos River, Texas
Larval, pupal and adult samples of Culoptila cantha, from a large riffle of the Brazos River in north-central Texas from January, 1995 to March, 1997, indicated a predominately trivoltine cycle during both years; the over-wintering generation spanned 6-7 months and warm-season generations spanned 2-3 months. Eggs, larvae of all instars, larval cases, case reconstruction progression and behavior, pupae, and adults are described.
Advanced Molecular and Microbial Techniques: a Complete Laboratory Notebook
The purpose of this project is to produce a complete and thorough notebook that may be used to supplement laboratory coursework. Its intent is to be used primarily by the students to aid them in understanding background information and the proper laboratory procedures involved in various types of experiments. The laboratory notebook is a summation of all the experiments and procedures used in the six-credit hour Advanced Microbial and Molecular Biology (BIOL 5160) course offered during the summer semester at the University of North Texas. This class is a team taught effort by Professors O'Donovan and Kunz. The course is constructed as an intensive practice exercise to teach the student about gene mutations, biosynthetic pathways, preparation and analysis of plasmid DNA, and many other topics included in the notebook.
Biology and Energetics of Tropisternus Lateralis Nimbatus (SAY) (Coleoptera: Hydrophilidae) in a Playa on the Southern High Plains of Texas and Aquatic Coleoptera Diversity from Seven Playas on the Southern High Plains of Texas
A study of the biology of Tropisternus lateralis, a hydrophilid beetle, was conducted during the flood period of a single playa on the Southern High Plains of Texas from early June 1995 through early September 1995. Mechanism of colonization, tolerance/avoidance to drought, larval density, and secondary production were analyzed. T. lateralis colonized playas from surrounding aquatic habitats and avoided drought through aerial dispersion. Once in the playa, larval density increased over time. Secondary production was 1.31 g/m2/.25 yr. In addition, aquatic Coleoptera diversity was studied in seven playas on the Southern High Plains of Texas. A total of twenty three species were identified from the study region. Nine species not reported in playa literature were identified.
Regulation of Escherichia coli pyrBI Gene Expression in Pseudomonas fluorescens
Pseudomonas fluorescens does not appear to regulate the enzymes of de novo pyrimidine biosynthesis at the level of gene expression. Little or no apparent repression of pyr gene expression is observed upon addition of exogenous pyrimidines to the growth medium. The Escherichia coli pyrBI genes for aspartate transcarbamoylase (ATCase) were sized down and cloned into the broad host range plasmid, pKT230. Upon introduction into a P.fluorescenspyrB mutant strain, ATCase showed repression in response to exogenously fed pyrimidine compounds. Thus, it was possible to bring about changes in pyrimidine nucleotide pool levels and in transcriptional regulation of gene expression at the same time.
The Response of Aquatic Insect Communities and Caged In situ Asiatic Clams (Corbicula fluminea) to Dechlorinated Municipal Effluent in the Trinity River in North Texas
Dischargers to the Trinity River in North Texas were required to dechlorinate their effluents in 1990-91. Field surveys were conducted above and below an outfall to determine the response of resident immature insects and caged in situ juvenile Asiatic clams to chlorinated and dechlorinated effluent. Within six months after dechlorination began, insect community composition and C. fluminea survival significantly improved at stations below the outfall. Significantly lower clam growth within one mile below the dechlorinated effluent indicated the presence of non-chlorine toxicants. Effects from chlorinated and dechlorinated effluent exposure were comparable between Ceriodaphnia dubia lab tests and in situ C. fluminea.
Comparison of Remediation Methods in Different Hydrogeologic Settings Using Bioplume II
A contaminant fate and transport computer model, Bioplume II, which allows simulation of bioremediation in ground water systems, was used to compare the effects of 11 remediation scenarios on a benzene plume. The plume was created in three different hydrogeologic settings from the simulation of an underground gasoline storage tank leak.
Short Term Effects of External Electric Fields on Electrical Activity of the Pineal Gland in Rats
The effects of short term exposure (5 minutes) to EEFs at relatively high dosages (10, 25, 39, kV/m) on the electrical activity in rat pineal glands was studied. Daytime and nighttime recordings were taken from an implanted microelectrode in the gland. The data show that (1) both the activity and frequency were enhanced when the animals were exposed to EEFs at 39 kV/m continuously and discontinuously; (2) the later condition yielded a sustained increase (36%) whereas the former a brief (10 sec) increase. This enhancement was statistically significant under both conditions (day and night). The effects observed were thought to be due to membrane alterations either in the pineal gland itself or in the neural inputs to the gland.
Primary Productivity and Nutrient Relationships in Garza-Little Elm Reservoir
A large, multi-basin, reservoir (Garza-Little Elm Reservoir) in north central Texas was studied to determine the relative effects of various parameters on primary productivity. The basins were impounded several years apart,thus allowing the influence of age on water chemistry and biota to be considered. Another principal influence on water quality was secondary sewage effluent that entered one basin from a nearby source.
Biological Nitrogen Fixation in Two Southwestern Reservoirs
This investigation has determined the presence of biological nitrogen fixation in two reservoirs in the southwestern United States: Lake Arlington and Lake Ray Hubbard. Subsequent tests have gathered baseline data on the effects of various biological, chemical, and physical parameters on in situ nitrogen fixation in these reservoirs. Of specific importance is the relationship between nitrogen fixation arid occasional blooms of blue-green algae which produce such problems as testes and odors in these water-supply impoundments.
Assembly of Pseudomonas putida Aspartate Transcarbamoylase and Possible Roles of the PyrC' Polypeptide in the Folding of the Dodecameric Enzyme
Aspartate transcarbamoylase (ATCase) of Pseudomonas putida consists of two different polypeptides, PyrB and PyrC' (Schurr et al, 1995). The role of the PyrC' and the assembly of PyrB and PyrC' have been studied. The ATCase made in vitro of P.putida PyrB with P.putida PyrC', and of E.coli PyrB with P.putida PyrC ' were generated under two different conditions, denaturation and renaturation, and untreated. It was found that PyrC' plays a role in the enzymatic regulation by ATP, CTP and UTP. In addition to playing a role in substrate binding, the PyrB polypeptide is also involved in effector binding (Kumar et al., manuscript in preparation). The most energetically preferred form of the P.putida WT is a dodecamer with a molecular mass of 480 kDa. The ratio between the PyrB and the PyrC' is 1:1. In studies of nucleotide binding, it was discovered that the P.putida PyrB was phosphorylated by a protein kinase in the cell extract. In the presence of 20 mM EDTA, this phosphorylation was inhibited and the inhibition could be overcome by the addition of divalent cations such as Zn2+ and Mg2+. This result suggested that the phosphorylation reaction required divalent cations. In the CAD complex of eukaryotes, phosphorylations of the CPSase and the linker region between ATCase and DHOase did not occur in the presence of UTP and it was hypothesized (Carrey, 1993) that UTP and phosphorylation(s) regulated the conformational change in the enzyme complex. Therefore, the same idea was approached with P.putida ATCase, where it was found that 1.0 mM UTP inhibited the phosphorylation of PyrB by more than 50%. These results suggested that the regulation of the conformational change of the P.putida ATCase might be similar to that of CAD. Furthermore, peptide mapping for phosphorylation sites was performed on P.putida ATCase WT, WT --11 amino acids and WT --34 amino acids from the N-terminus of the PyrB polypeptide. The results showed that the phosphorylation sites were located on the fragment that contained amino acid number-35 to amino acid number-112 from the N-terminus of the PyrB polypeptide.
Physical and Functional Characterization of the xy1XYZ Region From TOL Plasmid pDK1 and its Associated Downstream Regulatory Elements
The nucleotide sequence for the pDKl TOL plasmid region encoding toluate-1,2-dioxygenase (Xy1XYZ, TO) was determined. TO is the first enzyme in the meta-cleavage operon, responsible for the conversion of toluates and benzoates to their carboxy-substituted diols. DNA sequence analysis revealed the presence of three open reading frames (ORF). The three ORFs correspond to xylX (1353 bp), xylY (486 bp) and xylZ (1008 bp), encoding predicted protein products of 51370 Da, 19368 Da and 36256 Da, respectively.
Biochemical Identification of Molecular Components Required for Cyanide Assimilation in Pseudomonas fluorescens NCIMB 11764
Utilization of cyanide as a nutritional nitrogen source in P. fluorescens NCIMB 11764 was shown to involve a novel metabolic mechanism involving nonenzymatic neutralization outside of cells prior to further enzymatic oxidation within. Several cyanide degrading enzymes were produced by NCIMB 11764 in response to growth or exposure to cyanide, but only one of these cyanide, oxygenase (CNO), was shown to be physiologically required for assimilation of cyanide as a growth substrate.
Analysis of the Trypanosoma brucei Genome and Identification and Characterization of a Gene Family Encoding Putative EF-Hand Calcium-Binding Proteins
The flagellum of Trypanosoma brucei contains a family of antigenically related EF-hand calcium-binding proteins which are called the calflagins. Genomic Southern blots indicated that multiple copies of calflagin genes occur in T brucei. All of the copies were contained in a single 23 kb Xhol-Xhol fragment. Genomic fragments of 2.5 and 1.7 kb were cloned that encoded calflagin sequences. Two new members of the calflagin family were found from genomic clone sequences. The deduced amino acid sequences of the genomic clones showed the calflagin genes were arranged tandemly along the genomic fragments and were similar to previously described calflagins. The calflagin genes were related by two unrelated 3' flanking sequences. An open reading frame that was unrelated to any calflagin was found at the 5' end of the 2.5 kb genomic fragment. Each encoded protein (~24,000u) contained three EF-hand calcium-binding motifs and one degenerate EF-hand motif. In general, variability among the T. brucei calflagins is greater than related proteins in T. lewisii and T. cruzi. This variability results from amino acid substitutions at the amino and carboxy termini, and duplication of internal segments.
Characterization of Arthrobacter Globiformis Aspartate Transcarbamylase Concentrations of Substrates
This thesis consists of one major section with two subsections. The first subsection investigates the activity of Arthrobacter globiformis aspartate transcarbamylase's specific activity with increasing concentrations of the enzyme's substrate. Dihydroorotase (DHOase) activity was also measured with increasing concentrations of the substrate dihydroorotate. The second subsection collected data in order to classify the enzyme, resulting in a classification into the category of class A ATCases with bifunctional ATCase-DHOase complexes. The thesis provides evidence to broaden understanding of the ATCase and DHOase enzymes for members of the family that Arthrobacter belongs to.
Bioconcentration and Morphological Effects of Triclosan on Three Species of Wetland Plants
Triclosan (TCS) is an antimicrobial compound found in several types of common household products. After being washed down the drain, TCS will then end up in the local watershed. Although numerous studies have been conducted to evaluate the fate and effects of TCS in aquatic environments, there have been no studies evaluating the role arbuscular mycorrhizal fungi (AM) play in a plants response to TCS exposure. Three species of wetland plants native North Texas were inoculated with AM spores and exposed to 0, 0.4 g/L and 4.0 g/L TCS concentrations. Root morphology of E. prostrata and S. herbacea showed AM and exposure responses. S. herbacea produced the greatest amounts biomass and TCS bioaccumulation, in all but one treatment. It also displayed opposing results to E. prostrata in measures of root length, root surface area, relative root mass, relative shoot mass and shoot:root ratio. TCS root tissue concentrations increased with increased exposures for both E. prostrata and S. herbacea. Even though E. prostrata had the lowest levels in each measure of biomass production, it had the highest amount of root TCS bioaccumulation in the AM inoculated 4.0 g/L treatment. H. laevis was between the other two species in terms of biomass production, and did not demonstrate any exposure or inoculation effects in morphology or TCS accumulation. Overall, no clear patterns were detected, which highlights the fact that further study is required to completely understand the effects compounds like TCS can have on plant community structure, and ultimately ecosystem function.
Examination of the Relationship Between Glucuronic Acid and Vascular Damage in Rats
The goal of this experiment was to examine the role of glucuronic acid in the development of vascular damage in the kidneys and retinas of diabetic individuals. Glucuronic acid was provided to rats in their water at various concentrations in order to increase plasma levels of the compound. Kidneys and retinas were excised and compared to control specimens using microscopy to determine the effect of elevated blood glucuronic acid levels on the occurrence of microaneurysms in renal capillary networks. No differences were seen between the treatment and control groups. Further study needs to be conducted to determine a more suitable time frame for this experiment.
Aging Is a Determinant in Anoxia Stress Tolerance in Caenorhabditis Elegans
Oxygen availability is critical for survival for most organisms. The nematode, C. elegans, has been useful for studying genetic regulation of anoxia tolerance due to the oxygen deprivation response mechanisms shared with other metazoans. Studies examining long-term anoxia (72h, LTA) tolerance have only been conducted at adult day 1. To investigate the effect of aging on anoxia tolerance wild-type and mutant strains were exposed to LTA between adult day 1 and day 9. Wild-type isolates and daf-16(mu86) (FOXO transcription factor regulated by insulin-signaling) and aak-2(gt33) (catalytic subunit of AMP-activated protein kinase) strains were anoxia sensitive at day 1 and displayed increased LTA tolerance with aging correlated with reproductive senescence followed by a decline in survivorhsip through day 9. The daf-2(e1370) (insulin receptor homologue of C. elegans), glp-1(e2141) (a lin-12/Notch receptor) and fog-2(q71) (required for spermatogenesis) strains were LTA-tolerant through day 5. I conclude that aging influences LTA-tolerance in a strain- and age-dependent manner. In addition to being LTA-tolerant the daf-2(e1370) and glp-1(e2141) strains have a longevity phenotype that is suppressed by loss of kri-1 or daf-12. While loss of kri-1 did not suppress the LTA-tolerant phenotype of glp-1(e2141) at day 1 the portion of impaired survivors increased at day 3 and by day 5 tolerance was suppressed. Similarly, when exposed to 4 days of anoxia the glp-1(e2141);daf-12(rh41rh611) double mutant had a reduced survivor rate at all ages analyzed compared to glp-1(e2141) controls. To better understand formation of an anoxia-tolerant physiology I exposed adults to one or more 24h bouts. Recurrent bouts increased LTA tolerance in wild-type hermaphrodites in a dose-dependent manner. Bout-treated daf-16(mu86) animals had increased survival rate compared to controls yet maximum survival remained below age-matched wild-type. Anoxia bouts decreased LTA-tolerance in aak-2(gt33) mutants, indicating the requirement for ATP regulation in establishing an LTA-tolerant phenotype. These data support the idea that anoxia tolerance is multi-factorial and influenced by environment, metabolism, food, reproduction, sex phenotype and likely additional factors.
Evaluating the Habitat Requirements of the Golden Orb Mussel (Quadrula Aurea) for Conservation Purposes
Many freshwater mussels are imperiled, due to a number of interrelated factors such as habitat alteration, degradation of water quality, and impoundments. The Golden Orb mussel (Quadrula aurea, I. Lea, 1859) is endemic to the state of Texas and is currently a candidate for the endangered species list, as the number of known populations has been declining in recent years. Little is currently known about Q. aurea aside from basic distribution data. This study is focused on evaluating a combination of macro-habitat and micro-habitat variables to determine their influence on the distribution and density of this species. Macro-habitat variables, including dominant land cover, surface geology, and soil erodibility factor, did not have a significant relationship with mussel distributions. The best model of micro-habitat variables that impacts the Q. aurea distributions is comprised of relative substrate stability (RSS) at moderate flows and current velocity at low flows. For all mussel species in this study, current velocity at low flows is the primary variable that influences distribution. Q. aurea are associated with habitats where larger sediment particles (large gravel and cobble) help to stabilize the substrate in areas with higher current velocities. An understanding of the preferred habitats for Q. aurea can be used to help focus conservation efforts and practices.
Primary Cilia in the Oligodendrocyte Lineage
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oligodendrocytes migrate from the corpus callosum into the overlying cortex. The incidence of cilia did not change markedly across age groups, and did not vary consistently with the number of processes per cell, which was used as an indication of the maturation stage of OPCs and young OLs. The mean percent of Olig1 immunopositive (Olig1+) cells having cilia across ages was 33.1% + 16.5%, with all ages combined. In O4+ cells of these mice, 56.7 + 3.6% had primary cilia. If it is the case that adult OLs do not have cilia, the point in the lineage when primary cilia are lost is still unknown. Adult mice that had been injected with cyclopamine to block cilia-dependent Shh signaling were examined to determine whether the rate of generating new OPCs was influenced. In the CC of control mice, the numerical density of Olig1+/BrdU+ cells was 1.29 + 0.07/mm2 was reduced to 0.68 + 0.38/mm2 in the cyclopamine-injected group, and the numerical density of all BrdU+ cells (including both Olig1+ and Olig1- cells) of 4.55 + 1.50/mm2 in the control group was reduced to 3.14 + 1.27/mm2 in the cyclopamine-injected group. However, there were only 2 mice in each group and the differences were not statistically significant.
Genetic Interest Assessment
Genetics is becoming increasingly integrated into peoples' lives. Different measures have been taken to try and better genetics education. This thesis examined undergraduate students at the University of North Texas not majoring in the life sciences interest in genetic concepts through the means of a Likert style survey. ANOVA analysis showed there was variation amongst the interest level in different genetic concepts. In addition age and lecture were also analyzed as contributing factors to students' interest. Both age and lecture were evaluated to see if they contributed to the interest of students in genetic concepts and neither showed statistical significance. The Genetic Interest Assessment (GIA) serves to help mediate the gap between genetic curriculum and students' interest.
Exploring the Evolutionary History of North American Prairie Grouse (Genus: Tympanuchus) Using Multi-locus Coalescent Analyses
Conservation biologists are increasingly using phylogenetics as a tool to understand evolutionary relationships and taxonomic classification. The taxonomy of North American prairie grouse (sharp-tailed grouse, T. phasianellus; lesser prairie-chicken, T. pallidicinctus; greater prairie-chicken, T. cupido; including multiple subspecies) has been designated based on physical characteristics, geography, and behavior. However, previous studies have been inconclusive in determining the evolutionary history of prairie grouse based on genetic data. Therefore, additional research investigating the evolutionary history of prairie grouse is warranted. In this study, ten loci (including mitochondrial, autosomal, and Z-linked markers) were sequenced across multiple populations of prairie grouse, and both traditional and coalescent-based phylogenetic analyses were used to address the evolutionary history of this genus. Results from this study indicate that North American prairie grouse diverged in the last 200,000 years, with species-level taxa forming well-supported monophyletic clades in species tree analyses. With these results, managers of the critically endangered Attwater's prairie-chicken (T. c. attwateri) can better evaluate whether outcrossing Attwater's with greater prairie-chickens would be a viable management tool for Attwater's conservation.
Effects of Peripheral Nerve Injury on the Cells of the Dorsal Root Ganglion: a Role for Primary Cilia
Primary cilia are ubiquitous sensory organelles found on most cell types including cells of the dorsal root ganglia (DRG). The DRG are groups of peripheral neurons that relay sensory information from the periphery to the CNS. Other cell types in the DRG include a type of glial cell, the satellite glial cells (SGCs). The SGCs surround the DRG neurons and, with the neurons, form functional sensory units. Currently are no reports describing the numbers of DRG cells that have cilia. We found that 26% of the SGCs had primary cilia. The incidence of cilia on neurons varied with neuron size, a property that roughly correlates with physiological characteristics. We found that 29% of the small, 16% of the medium and 5% of the large neurons had primary cilia. Primary cilia have been shown to have a role in cell proliferation in a variety of cell types. In some of the cells the cilia mediate the proliferative effects of Sonic hedgehog (Shh). In the CNS, Shh signaling through primary cilia affects proliferation during development as well as following injury, but no studies have looked at this function in the PNS. The SGCs and neurons of the DRG undergo complex changes following peripheral nerve injury such as axotomy. One marked change seen after axotomy is SGC proliferation and at later stages, neuronal death. We found that following axotomy there is a significant increase in the percentage of SGCs with primary cilia. We also found a significant increase in the percentage of medium-sized neurons with primary cilia. In other experiments we tested the idea that Shh plays a role in SGC proliferation. When Shh signaling was blocked following axotomy we found decreased proliferation of SGCs. This is the first report of a change in the percentage of cells with cilia following injury in the PNS, and the first report of a role for Shh in SGC proliferation following axotomy.
Somatostatin Receptors on Neuronal Cilia: Evidence for Neuroprotection
Primary cilia are essential in brain development, as mediators of sonic hedgehog signaling. However, their role in mature neurons remains elusive. One means to elucidate their function may be to investigate the function of the somatostatin type 3 receptor (SstR3), which is concentrated on the primary cilia of neurons. The inhibitory and anticonvulsant properties of somatostatin suggest that ciliary SstR3 might protect neurons against excitotoxicity, as seen in epileptic seizures. C57BL/6 wild type (wt) and SstR3 knockout mice were administered vehicle or epileptogenic agents kainic acid (KA) or pentylenetetrazole. Seizure behaviors were rated on seizure severity scales. KA-induced seizure behaviors were more severe in SstR3 mutants than in wt. Correspondingly, the mutants showed greater reactive gliosis, as indicated by increased numbers of GFAP immunoreactive (GFAP(+)) astrocyte processes. In addition, seizure severity was associated with a greater percentage of neural stem cells having an ACIII(+) cilium. Following injections of pentylenetetrazole, SstR3 mutants reached maximum seizure levels faster than wt. These results support the hypothesis that ciliary SstR3 are neuroprotective in mature neurons, and may provide a new avenue for the treatment of seizures.
Clustering Algorithms for Time Series Gene Expression in Microarray Data
Clustering techniques are important for gene expression data analysis. However, efficient computational algorithms for clustering time-series data are still lacking. This work documents two improvements on an existing profile-based greedy algorithm for short time-series data; the first one is implementation of a scaling method on the pre-processing of the raw data to handle some extreme cases; the second improvement is modifying the strategy to generate better clusters. Simulation data and real microarray data were used to evaluate these improvements; this approach could efficiently generate more accurate clusters. A new feature-based algorithm was also developed in which steady state value; overshoot, rise time, settling time and peak time are generated by the 2nd order control system for the clustering purpose. This feature-based approach is much faster and more accurate than the existing profile-based algorithm for long time-series data.
Beta-adrenergic Blockade Via Atenolol and Its Effects on Blood Pressure, Heart Rate, and Renal Morphology in the Developing Chicken Gallus Gallus Domesticus
Chicken embryos were chronically exposed to the ?1- blocker atenolol during one of three stages: mesonephros (E7-E9), mesonephros-metanephros (E11-E13), or metanephros (E15-E17). Mesonephros group hearts were larger than all other groups (P < 0.01). Mesonephros and metanephros group kidneys were larger than all remaining groups (P < 0.0001). The mesonephros group nephron number was ~40% lower than control values (P = 0.002). Glomerular areas were 26% and 18% larger than the control group in the mesonephros and metanephros groups, respectively (P < 0.001). These data suggest an E7-E9 critical window of cardiovascular and renal development for atenolol. Acute atenolol exposure in E15 embryos showed an increase in mean arterial pressure with all but the highest dose. All doses significantly decreased heart rate.
Chronic Hypoxia and Hyperoxia Modifies Morphology and Vegf Expression of the Lungs of the Developing Chicken (Gallus Gallus Domesticus)
This study determines effects of oxygen levels on morphology and VEGF expression of developing chicken lungs following incubation in normoxia (21% O2), hypoxia (15% O2) or hyperoxia (30% O2), until developmental days 16 or 18. Lung morphology was assessed using light microscopy, while VEGF expression was determined with ELISA. In hypoxia, the proportion of parabronchial tissue and parabronchi including lumina increased from day 16 to 18 (61 to 68% and 74.2 to 82.2%, respectively). Non-parabronchial tissue was higher in hypoxia than in hyperoxia on day 16 (26 to 20%). However, by day 18, there were no differences between groups. VEGF expression was 33% higher in hypoxia than in hyperoxia on day 16 (736 vs. 492 pg/ml). On day 18, VEGF expression was 43% higher in hyperoxia than in normoxia (673 to 381pg/ml), and remained elevated by 40% in hypoxia over normoxia (631 pg/ml). VEGF may be a mechanism by which parabronchial tissue is stimulated from day 16 to 18 following exposure to chronic hypoxia.
Pressure-Flow Relationships in the Isolated Cerebral Circulation of the Dog
The purpose of this investigation is to determine the pressure-flow relationships in the isolated canine cerebral vascular bed. These relationships in vessels which supply an organ surrounded by bone are theoretically influenced by limiting factors which are not present in those vessels surrounded by soft tissue. An evaluation of the extent of these limitations is essential to thorough understanding of the dynamics of the cerebral vascular bed.
Effects of X-Irradiation on Water and Ion Flux in Isolated Roots
Due to the relatively small amount of work concerning radiation, it was thought feasible to use ionizing radiation as a tool to study the relationship between water and salt flux in isolated root systems. Moreover, the more quantitative potometric method lends itself well to such a study, since the two processes can be followed simultaneously. the aims of this study, therefore, were 1) to determine effects of X-irradiation on water, calcium and potassium flux in excised onion roots; 2) to determine the dose levels required for producing permeability changes; 3) to investigate the nature of radiation damage to root systems; and 4) to attempt to shed light on the relation between water transport and ion movement in root systems.
A Study of a Branchiobdellid from Denton County, Texas
In this study, branchiobdellids were collected from crayfish captured from two adjacent sites in Denton County, Texas. Identification of the branchiobdellid, Cambarincola vitrea Ellis, was first made and then work was extended to include several topics of ecological interest.
The Autecology of Celtis Laevigata in Flood Plain Forests of Denton County, Texas
This thesis describes the present nature of one facet of some of the flood plain forest stands in Denton County, Texas. The specific purpose was to demonstrate the presence or absence of difference between the Celtis laevigata (commonly known as the hackberry, southern hackberry or sugarberry) populations in stands on Denton Creek and Elm Fork of the Trinity River.