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open access

L-asparaginase II Production by Escherichia coli

Description: Growth of Escherichia coli A-l under aerobic conditions in an enriched medium with a total amount of 0.2 per cent glucose was biphasic and asparaginase II activity was detected after depletion of ammonia from the growth medium in the second phase of growth. Glucose was exhausted two hours before ammonia and three hours before asparaginase II activity was detected. The concentration of 3',5'-cyclic adenosine monophosphate was found to fluctuate when the dissolved oxygen in the medium reached a l… more
Date: May 1985
Creator: Johnson, Terrance L. (Terrance Lewyne), 1950-
Partner: UNT Libraries
open access

Biological and Toxicological Responses Resulting from Dechlorination of a Major Municipal Wastewater Treatment Plant Discharge to the Trinity River

Description: Federal regulations such as the Clean Water Act (P.L. 92-500), and its amendments, direct the Environment Protection Agency (EPA) to implement programs to control the releases of conventional pollutants and toxics into the waterways of the United States. The EPA began requiring treatment plants to conduct toxicity tests (biomonitoring) of their effluent discharges. To control toxicity caused by chlorination of wastewater discharges, the EPA also began requiring some treatment facilities to dech… more
Date: August 1995
Creator: Guinn, Richard J. (Richard Joe)
Partner: UNT Libraries
open access

Cardiovascular Fetal Programming in Quail (Colinus virginianus), An Avian Comparative Model

Description: The consequences of early embryonic insults and how they affect subsequent life reflects the emerging concept of "fetal programming". The aim of this project is to study the effects of embryonic insults as they subsequently manifest themselves in adults, with emphasis on the heart and vasculature. My experiments establish that fetal programming operates on the bobwhite quail inducing similar changes as those observed in mammalians and other birds. The quail's fast development provides reliable … more
Date: December 2016
Creator: Flores Santin, Josele R.
Partner: UNT Libraries
open access

Construction of a Pseudomonas aeruginosa Dihydroorotase Mutant and the Discovery of a Novel Link between Pyrimidine Biosynthetic Intermediates and the Ability to Produce Virulence Factors

Description: The ability to synthesize pyrimidine nucleotides is essential for most organisms. Pyrimidines are required for RNA and DNA synthesis, as well as cell wall synthesis and the metabolism of certain carbohydrates. Recent findings, however, indicate that the pyrimidine biosynthetic pathway and its intermediates maybe more important for bacterial metabolism than originally thought. Maksimova et al., 1994, reported that a P. putida M, pyrimidine auxotroph in the third step of the pathway, dihydroorot… more
Date: August 2003
Creator: Brichta, Dayna Michelle
Partner: UNT Libraries
open access

Ecotoxicological Investigations in Effluent-Dominated Stream Mesocosms

Description: The University of North Texas Stream Research Facility (UNTSRF) was designed to examine contaminant impacts on effluent-dominated stream ecosystems. Stream mesocosms, fed municipal effluent from the City of Denton, TX, Pecan Creek Water Reclamation Plant (PCWRP), were treated with 0, 15 or 140 µg/L cadmium for a 10-day study in August 2000. Laboratory toxicity test and stream macroinvertebrate responses indicated that cadmium bioavailability was reduced by constituents of effluent-dominated str… more
Date: December 2002
Creator: Brooks, Bryan W.
Partner: UNT Libraries
open access

Effects of 4-Chloroglutaranilic Acid on Growth and Development of Sunflower Seedlings

Description: The potential growth-regulating compound 4-chloroglutaranilic acid (CGA) was tested in whole-plant bioassay systems which utilized sunflower seedlings (Helianthus annuus, L.). Test systems included the growth of plants in soil , solid inert (Vermiculite) substrate, and hydroponic (Seed-Pak) pouches.
Date: August 1972
Creator: Larsen, Stephen P. (Stephen Page), 1933-
Partner: UNT Libraries
open access

The Effects of Organic Surface Amendments on Soil Nutrients and Initial Tree Establishment

Description: 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 appli… more
Date: May 1999
Creator: Thuesen, Kevin (Kevin Andrew)
Partner: UNT Libraries
open access

A Floristic Study of the Woody Vegetation of the North American Cross Timbers

Description: This research represents the first systematic collection of the woody plants throughout the Cross Timbers. It provides the first keys to these plants in their vegetative condition, plant descriptions, distribution maps, and some quantitative measurements used for descriptive purposes. Descriptions of the woody plants were constructed as an aid in verification after a specimen has been identified by use of the keys. The measurements given pertain only to the woody plants as they occur in the Cro… more
Date: December 1974
Creator: Harrison, Thieron Pike
Partner: UNT Libraries
open access

Forest Landscape Dynamics: a Semi-Markov Modeling Approach

Description: A transition model (MOSAIC) is used to describe forest dynamics at the landscape scale. The model uses a semi-Markov framework by considering transition probabilities and Erlang distributed holding times in each transition. Parameters for the transition model are derived from a gap model (ZELIG). This procedure ensures conceptual consistency of the landscape model with the fine scale ecological detail represented by the forest gap model. Spatial heterogeneity in the transition model is driven b… more
Date: August 1997
Creator: Ablan, Magdiel
Partner: UNT Libraries
open access

A geospatial tool for assessing potential wildland fire risk in central Texas.

Description: Wildland fires in the United States are not always confined to wilderness areas. The growth of population centers and housing developments in wilderness areas has blurred the boundaries between rural and urban. This merger of human development and natural landscape is known in the wildland fire community as the wildland urban interface or WUI, and it is within this interface that many wildland fires increasingly occur. As wildland fire intrusions in the WUI increase so too does the need for too… more
Date: August 2005
Creator: Hunter, Bruce Allan
Partner: UNT Libraries
open access

The Immune Response of Guinea Pigs as Influenced by Hypobaric Pressure and Normoxic Environment (Part I); Membrane Filter-Fluorescent-Antibody Method for Detection and Enumeration of Bacteria in Water (Part II)

Description: In this work experimental design and tests were established to determine whether antibody production in guinea pigs injected with a bacterial antigen is Influenced by the environment of simulated high altitude with normoxic conditions. Hematological and electrophoretic studies were simultaneously run with the antibody determinations as a check on related responses of the animals.
Date: August 1969
Creator: Reeder, Dennis James
Partner: UNT Libraries
open access

Immunofluorescence as a Method for the Rapid Identification of Streptococcus Faecalis in Water

Description: The development and refinement of FA has been adequately investigated with major emphasis on pathogenic microorganisms. The development of this technique has reduced both the time and number of biochemical tests necessary to identify a diversity of organisms. The organisms included are the protozoans, as described by Goldman (1953 and 1957) and by Ingram (1961), viruses, as reported by Liu (1955a) and Burgdorfer and Lackman (1960a), pathogenic bacteria which have been investigated by Moody, Gol… more
Date: August 1970
Creator: Abshire, Robert Louis
Partner: UNT Libraries
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Impact of a Genetically Engineered Probiotic Therapy and IGF-1 Genomics in the PAHenu2 Mouse Model of PKU

Description: Absence of functional phenylalanine hydroxylase results in phenylketonuria (PKU). Viable treatments remain few, expensive and secondary conditions such as osteopenia occur in most PKU patients. Objective 1: Given the recently described roles of gut microbes to aid host digestion, an orally administered genetically engineered probiotic as the delivery vehicle for enzyme replacement therapy was created. The engineered probiotic, pHENOMMenal, produced phenylalanine ammonia lyase with significant… more
Date: December 2015
Creator: Durrer, Katherine Elaine
Partner: UNT Libraries
open access

The Impact of Developmental Stress on Cardiovascular Physiology of Two Archosaur Species: American Alligator (Alligator mississippiensis) and Domestic Chicken (Gallus gallus)

Description: Crocodilians and birds comprise sister taxa of archosaurs, the development of these vertebrates occurs within an egg case that leaves developing embryos susceptible to fluctuations in the nesting environment. Studies suggest that sub-optimal conditions alter morphological growth and cardiovascular physiology. Regulation of the cardiovascular system is immature in the subjects studied, and embryos may rely on humoral rather than neural control of the cardiovascular system. The primary focus of t… more
Date: December 2014
Creator: Tate, Kevin B.
Partner: UNT Libraries
open access

Impacts of the Pyrethroid Insecticide Cyfluthrin on Aquatic Invertibrate Populations in Outdoor Experimental Tanks

Description: The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were… more
Date: May 1992
Creator: Johnson, Philip C. (Philip Charles)
Partner: UNT Libraries
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Investigating the Ability of Pseudomonas aeruginosa pyrE Mutants to Grow and Produce Virulence Factors

Description: Pseudomonas aeruginosa are medically important bacteria that are notorious for causing nosocomial infections. To gain more knowledge into understanding how this organism operates, it was decided to explore the pyrimidine biosynthetic pathway. Pyrimidine synthesis, being one half of the DNA structure, makes it a very important pathway to the organism’s survivability. With previous studies being done on various genes in the pathway, pyrE has not been studied to the fullest extent. To study the fu… more
Date: December 2014
Creator: Niazy, Abdurahman
Partner: UNT Libraries
open access

Investigation of Pyrimidine Salvage Pathways to Categorize Indigenous Soil Bacteria of Agricultural and Medical Importance and Analysis of the Pyrimidine Biosynthetic Pathway's Enzyme Properties for Correlating Cell Morphology to Function in All Phases of Growth

Description: This dissertation comprises three parts and is presented in two chapters. Chapter 1 concerns Arthrobacter, a bacterium with an intriguing growth cycle. Whereas most bacteria exist as either a rod or coccus, this bacterium shares the rod/coccus lifestyle. It therefore seemed important to examine the growth regulatory pathways from the rod and coccus. The committed step, that catalyzed by aspartate transcarbamoylase (ATCase), in the pyrimidine biosynthetic pathway was chosen. The ATCase in Arthr… more
Date: May 2003
Creator: Meixner, Jeffery Andrew
Partner: UNT Libraries
open access

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

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 employ… more
Date: December 2001
Creator: Sparks, Christopher A.
Partner: UNT Libraries
open access

The Isolation and Characterization of a Hitherto Undescribed Gram-Negative Bacterium

Description: A unique undosciribed gramnegative rod is extensively characterized in this study. The cells of this unusual water isolate measure 1.2 X 6.5 microns, The most distinguishing characteristic of the bacterium is a polar tuft of 35-40 flagella that aggregate to function as a single organelle which is visible under phase contrast. Aging cells deposit poly- -hydroxybutyric acid granules which are bound by an inclusion membrane made up of four distinct layers. It also possesses an unusual exterior mem… more
Date: August 1972
Creator: Lassiter, Carroll Benson
Partner: UNT Libraries
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Landscape Ecological Characteristics of Habitat of the Red-cockaded Woodpecker

Description: Geographic information systems (GIS) technology was used to analyze factors influencing habitat use by an endangered species, the red-cockaded woodpecker. The study area was the western part of the Raven Ranger District of the Sam Houston National Forest, Texas. The factors considered included both structural characteristics and spatial relationships among stands of trees in the habitat.
Date: December 1993
Creator: Thomlinson, John Richard
Partner: UNT Libraries
open access

Light and Electron Microscope Studies on the Chemotherapeutic Effect of a Combination of Dimethyl Sulfoxide and Hematoxylin on a Transplantable Lymphosarcoma

Description: Investigations concerning the cellular response of tumor tissue to treatment with dimethyl sulfoxide and hematoxylin have not been reported. To establish the response of neoplastic tissue and cells to this combination of agents, this study was undertaken to determine the effects of dimethyl sulfoxide and hematoxylin on a transplantable lymphosarcoma in mice.
Date: January 1970
Creator: Rogers, Thomas D., 1939-
Partner: UNT Libraries
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