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.

The high susceptibility to infection in persons with Down Syndrome (DS) has led some investigators to explore the possibility of a defect in the immune system. Studies to date indicate no defect in humoral immunity suggesting that the defect might be in the cellular immune functions, but no specific defect has been found. Our investigation of the cellular immune system of adult DS patients was conducted by examining (1) the number and function of T-lymphocytes, (2) the phagocytic function of granulocytes, (3) the level of superoxide dismutase-1 (SOD-1) in leukocytes, and (4) the effects of SOD-1 on lymphocyte and granulocyte functions.

Resistance exercise (RE) training is a well-known and effective method for promoting increases in muscle mass and strength. A single bout of RE induces physiological disturbances that require coordinated activation of the immune system and intramuscular signaling in order to return the tissue to homeostasis and adapt to the RE challenge. On the other hand, acute binge alcohol consumption can affect the immune response to an inflammatory challenge, intramuscular anabolic signaling, and muscle protein synthesis, and the effects of alcohol on these processes are opposite that of RE. Furthermore, individuals who report more frequent exercise also report a greater frequency of binge drinking. However, few investigations exist regarding the effects of binge alcohol consumed after a bout of RE on RE-induced physiological changes and performance recovery. Therefore, the overarching purpose of the investigations contained within this dissertation was to investigate the effect of alcohol consumed after RE on the RE-induced changes in mTOR pathway signaling, muscle protein synthesis, inflammatory capacity, strength recovery, and power recovery. Although RE increased mTOR pathway signaling and inflammatory capacity after exercise and reduced maximal strength and explosive power the day after exercise, we observed no effects of alcohol (1.09 g ethanol∙kg-1 lean body mass, designed …

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.

Since Actinomycetes have been isolated from finished public drinking water, it is believed that the organisms are unaffected by the chlorination and flocculation of water treatment plants and pass as spores through the filters into the general distribution system. For this reason it was deemed imperative to study the toxic effects of these organisms.

Triclosan and triclocarban are antimicrobials found in numerous consumer products, while caffeine is the most commonly consumed stimulant by humans. This study was undertaken to determine the effects of triclosan, triclocarban, and caffeine on the development and physiology of amphibian larvae. LC50 values of triclosan and triclocarban were determined after 96 hours for three North American larval species: Acris crepitans blanchardii, Bufo woodhousii woodhousii, Rana sphenocephala, and for a common amphibian developmental model: Xenopus laevis. Amphibian larvae were most sensitive to triclosan and triclocarban exposure during early development based upon 96-hour LC50 values. Heart rates for X. laevis and North American larvae exposed to triclosan were variable throughout development. However, significantly lower heart rates were observed in all larvae exposed to triclocarban. Metabolic rates of X. laevis and R. sphenocephala larvae exposed to triclosan were significantly affected in larvae exposed to ½ LC50 and the LC50 concentration. Metabolic rates of X. laevis larvae exposed to triclocarban were significantly affected by exposure to ½ LC50 concentrations in three of four stages investigated. No significant differences were observed in North American larvae exposed to triclocarban. Tissue uptake, lipid uptake, tissue bioconcentration factor (BCF) and lipid BCF of triclosan and triclocarban were investigated …

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.

Twenty-two different unialgal clonal isolates have been obtained at random for experimental purposes over a period of about one year. Also, during this period, at least 12 other species or strains have been isolated into unialgal cultures which had not yet been identified and/or significantly cleared of heterotrophic contaminants.

This project focused on the relationship between instream flows and smallmouth buffalo (Ictiobus bubalus) recruitment in the Gulf Coastal Plain of Texas. The flow regime is the dominant factor in lotic systems and, consequently, the relationship between instream flows, including impacts to natural flow regimes, and life-history is a subject of growing interest. Smallmouth buffalo is a good model to investigate the relationship between river flows and variable interannual recruitment success of periodic life-history strategist fish species. Smallmouth buffalo were collected from the Brazos, Colorado, and Guadalupe Rivers of Texas, U.S.A., and otoliths were extracted from individuals in the field and sectioned and photographed in the lab. Photographs of sectioned otoliths were used to estimate age and thus the year in which the individual was spawned by counting back from the time of capture. Population age structure (i.e. a ‘state' or condition at a point in time) was used to infer effects of flow variation on a rates-based process (i.e. recruitment). After controlling for mortality using recruitment index values, interannual variation in recruitment was modeled using multiple components of the flow regime quantified as indicators of hydrologic alteration (IHA) variables based on daily discharge data from USGS gaging stations in …

Reductions in baroreflex responsiveness have been thought to increase the prevalence of orthostatic hypotension in endurance trained athletes. To test this hypothesis, cardiovascular responses to orthostatic stress, cardiopulmonary and carotid baroreflex responsiveness, and the effect of cardiopulmonary receptor deactivation on carotid baroreflex responses were examined in 24 men categorized by maximal aerobic power (V02max) into one of three groups: high fit (HF, V0-2max=67.0±1.9 ml•kg^-1•min^-1), moderately fit (MF, V0-2max=50.9±1.4 ml•kg^-1•min^-1), and low fit (LF, V0-2max=38.9±1.5 ml•kg^-1•min^-1). Orthostatic stress was induced using lower body negative pressure (LBNP) at -5, -10, -15, -20, -35, and -50 torr. Cardiopulmonary baroreflex responsiveness was assessed as the slope of the relationship between forearm vascular resistance (FVR, strain gauge plethysmography) and central venous pressure (CVP, dependent arm technigue) during LBNP<-35 torr. Carotid baroreflex responsiveness was assessed as the change in heart rate (HR, electrocardiography) or mean arterial pressure (MAP, radial artery catheter) elicited by 600 msec pulses of neck pressure and neck suction (NP/NS) from +40 to -70 torr. Pressures were applied using a lead collar wrapped about the subjects' necks during held expiration. Stimulus response data were fit to a logistic model and the parameters describing the curve were compared using two-factor ANOVA. The reductions CVP, …

Fetal programming results from stressors during fetal development and may influence the occurrence of disease later in life. Maternal nutritional status and/or environment can affect renal development by inducing limited nephron endowment at birth, which results in diseases such as hypertension and coronary heart disease in mammals. Birds are likely to be effective models for this process because, like mammals, they have high pressure cardiovascular systems, mammalian-type nephrons and are homeothermic. This project uses the chicken embryo to explore physiological responses of disrupted hydration state thereby providing insights into renal fetal programming. Under normal conditions the chorioallantoic membrane (CAM) and developing avian kidney work in unison to ensure a proper balance of ions and water within the egg. White leghorn chicken eggs were incubated at 37.5oC±0.5oC and either <35%, 55-60% (normal) or >85% relative humidity. Amniotic fluid serves as the drinking source for the embryo late in development; its composition is important to salt and water homeostasis. High amniotic fluid osmolality increased the blood osmolality for embryos exposed to low humidity incubation thereby indirectly influencing the renal developmental program of the embryos from this group. Indeed estimated filtering capacity was doubled in the low humidity group (6.77 ± 0.43 mm3) …

The present study sought to determine some morphological and physiological critical windows during very early development in zebrafish exposed to crude oil. I hypothesized that exposed zebrafish would present a decrease in survival rate and body mass, and an increase in routine oxygen consumption (ṀO2), and critical oxygen tension (PCrit). To test these hypotheses, zebrafish were acutely exposed (24 h) during different days of development (1 to 6 days post-fertilization, dpf) to different concentrations of high-energy water-accommodated fractions (HEWAFs). The endpoints of survival, body mass, routine oxygen consumption, and critical oxygen partial pressure were measured at 7 dpf. Survival rate decreased based on the exposure concentration but not as a function of the day of crude oil exposure. No significant effects were found in PCrit. Body mass was reduced by the different concentrations of HEWAF, with the size of the effect varying with exposure day, with the effect strongest on when exposure occurred at 2 and 3 dpf. Oxygen consumption (ṀO2) differed significantly depending upon the day of exposure in fish exposed to crude oil. Specifically, HEWAF exposure significantly increased ṀO2 in larvae exposed at 3 dpf (9.081 µmol O2/g/h, ±0.559) versus 2 dpf (6.068 µmol O2/g/h, ±0.652) and 6 …

Cardiac, metabolic and growth response of early-stage chicken embryos to perturbations in yolk environment was investigated. Also, effects of parental hypoxia exposure on hypoxia resistance, thermal tolerance and body length of zebrafish larvae were investigated. In the first study, thyroxine, triiodothyronine and testosterone produced differential effects on heart rate and development rate of chicken embryos during the first 4 days of development. Triiodothyronine caused a dose-dependent increase in heart rate when applied at 40 or 70 hours of age, while thyroxine caused a dose-dependent increase in heart rate when applied at 40 hours only. Testosterone and propyl-thiouracil (deiodinase antagonist) did not have an effect on heart rate. Development rate was not changed by thyroxine, triiodothyronine, testosterone or propyl-thiouracil, which suggested that heart rate changes did not result from changes in embryo maturity. In the second study, chicken embryos exposed to yolks of different bird species during early-stage embryonic development showed changes in heart rate, mass-specific oxygen consumption and body mass that scaled with the egg mass, incubation period length, and yolk triiodothyronine and testosterone levels of the species from which yolk was derived. In the third study, this phenomenon was investigated between layer and broiler chickens. Heart rate, oxygen consumption …

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 …

The problem in this investigation consists of, first, the procurement of several strains of Micrococcus pyogenes var. aureus; second, the comparison of the degree and rate of development of resistance of these organisms to terramycin; and, third, to study the morphological and physiological changes which occur during the development of resistance.

The Deepwater Horizon oil spill released millions of barrels of oil into the Gulf of Mexico, impacting economically and ecologically important fishes. Polycyclic aromatic hydrocarbons (PAHs) present in the oil have been shown to cause developmental impairments in early life stage fishes, such as morphological and behavioral changes related to eye formation and visual processing following PAH exposure. Prior research reported reduced eye growth in open water, pelagic species, as well as reduced photoreceptor-specific transcription factors associated with eye development following exposure to crude oil. Though changes in transcriptomic-level pathways associated with vision and visual processing have been reported, it has yet to be determined how these changes relate to physiological or behavioral-level effects in fish. Therefore, the present studies evaluated the effect of weathered crude oil on eye development and visual function in mahi-mahi, red drum, sheepshead minnow, and zebrafish larvae. Fish were assessed through several visually-mediated behavioral assays, analyzed histologically and immunohistologically, along with subsequent transcriptomic analyses and associated gene expression changes. Larvae exposed to crude oil experienced significantly reduced abilities to exhibit optomotor or optokinetic responses relative to controls, with associated reductions in retinal development. Furthermore, genes associated with eye development and phototransduction were downregulated, with subsequent …

Oxygen deprivation can be pathological for many organisms, including humans. Consequently, there are several biologically and economically relevant negative impacts associated with oxygen deprivation. Developing an understanding of which genes can influence survival of oxygen deprivation will enable the formulation of more effective policies and practices. In this dissertation, genes that influence adult anoxia survival in the model metazoan system, C. elegans, are identified and characterized. Insulin-like signaling, gonad function and gender have been shown to influence longevity and stress resistance in the soil nematode, C. elegans. Thus, either of these two processes or gender may influence anoxia survival. The hypothesis that insulin-like signaling alters anoxia survival in C. elegans is tested in Aim I. The hypotheses that gonad function or gender modulates anoxia survival are tested in Aim II. Insulin-like signaling affects anoxia survival in C. elegans. Reduction of insulin-like signaling through mutation of the insulin-like receptor, DAF-2, increases anoxia survival rates in a gpd-2/3 dependent manner. The glycolytic genes gpd-2/3 are necessary for wild-type response to anoxia, and sufficient for increasing anoxia survival through overexpression. Gonad function and gender both affect anoxia survival in C. elegans. A reduction of ovulation and oocyte maturation, as measured by oocyte flux, …

This thesis presents the results of an examination conducted to determine the status of mourning doves in Throckmorton County, Texas.

Metagenomics is the study of the totality of the complete genetic elements discovered from a defined environment. Different from traditional microbiology study, which only analyzes a small percent of microbes that could survive in laboratory, metagenomics allows researchers to get entire genetic information from all the samples in the communities. So metagenomics enables understanding of the target environments and the hidden relationships between bacteria and diseases. In order to efficiently analyze the metagenomics data, cutting-edge technologies for analyzing the relationships among microbes and communities are required. To overcome the challenges brought by rapid growth in metagenomics datasets, advances in novel methodologies for interpreting metagenomics data are clearly needed. The first two chapters of this dissertation summarize and compare the widely-used methods in metagenomics and integrate these methods into pipelines. Properly analyzing metagenomics data requires a variety of bioinformatcis and statistical approaches to deal with different situations. The raw reads from sequencing centers need to be processed and denoised by several steps and then be further interpreted by ecological and statistical analysis. So understanding these algorithms and combining different approaches could potentially reduce the influence of noises and biases at different steps. And an efficient and accurate pipeline is important to …

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

The estuarine sheepshead minnow (Cyprinodon variegatus) is the most eurythermic fish species, with a thermal tolerance window between 0.6°C and 45.1°C. However, little is known about the physiological mechanisms that allow this species to survive this temperature range. In order to understand how sheepshead minnow physiology is affected by temperature acclimation and acute changes in temperature, I conducted research on this species using a multi-level approach. I began at the organismal level, and examined the effects of these temperature changes on the sheepshead minnow's metabolic rate and swimming performance. The next chapter investigated the effects of changing temperatures on cardiac function (i.e., tissue/organ specific effects). In the final chapter, I conducted research at the sub-cellular level, and determined how mitochondrial bioenergetics / function is impacted by changing temperatures. This research shows that while sheepshead minnows are able to sustain heart function and mitochondrial respiration over a broad range of temperatures; they also display a plastic temperature response which is associated with the downregulation of standard metabolic rate and cardiac remodeling to maintain force generation. Collectively, these physiological responses may contribute to the sheepshead minnow's ability to maintain physiological and organismal function across a large temperature range.