UNT Libraries - 11 Matching Results

Search Results

Quantitation of Endogenous Nucleotide Pools in Pseudomonas aeruginosa

Description: Nucleotide pools were extracted and quantified from Pyr^+ and Pyr^- strains of P. aerucjinosa. Strains were grown in succinate minimal medium with and without pyrimidines, and nucleotides were extracted using trichloracetic acid (TCA; 6% w/v). The pyrimidine requirement was satisfied by uracil, uridine, cytosine or cytidine. Pyr^- mutants were starved for pyrimidines for two hours before nucleotide levels were measured. This starvation depleted the nucleotide pools which were restored to wild type levels by the addition of pyrimidines to the medium. When the pyrimidine analogue, 6-azauracil, known to inhibit OMP decarboxylase, was added to cultures of the wild type strain, the uridine and cytidine nucleotides were depleted to near zero. Thus, the nucleotide pool levels of Pseudomonas strains can be manipulated.
Date: August 1988
Creator: Entezampour, Mohammad

Effect of Calcium Channel Antagonists and Other Agents on Olfactory Reception

Description: The role of Ca++ in olfactory responses was investigated with inorganic and organic calcium channel antagonists. Electrophysiological responses to odorants were recorded from frog olfactory mucosa before and after aerosol application of different agents. Electroolfactogram responses were blocked by certain inorganic ions with the order of effectiveness Zn++ >Ln+++>Cd++>Ca++>Co++>Sr++>Mg++. Ba++ potentiated olfactory responses, and is known to potentiate calcium channel-mediated responses in other tissues. Certain local anesthetics which are thought to act through calcium channel blockade were inhibitory to olfactory responses, with the order of effectiveness being dibucaine>tetracaine>procaine. These data support the idea that Ca++ is involved in olfaction, perhaps acting as a current carrier and/or a second messenger. Preliminary experiments on channel localization were performed using a silicon-labeled amine. Attempts to localize the silicon label were inconclusive, although silicon was detected in the olfactory tissue.
Date: August 1985
Creator: Rosick, Edward R. (Edward Rudolph)

Effects of Water Source, Suspended Solids, and Acclimation on Biotransformation of 2 /4-Dichlorophenoxy Acetic Acid in Aquatic Systems

Description: In recent years there has been a great deal of scientific interest in processes that affect the fate of organic chemicals in the environment. one main reason for this increased interest is due to greater environmental concern over accidental or purposeful release of these chemicals into the environment by man. A major environmental concern is the increased use of pesticides over the last few years. In the thirty years prior to 1978 the use of pesticides has increased by a factor of forty (Ridgeway et al., 1978). Recently the use of herbicides has been increasing, but that of insecticides has stabilized (Willis, 1983). Detectable amounts of organic pesticides can be found in many areas of the biosphere. For toxic organic chemicals to be used safely, researchers must have a clear understanding of the fate and persistence of these chemicals when they are released into the environment. This understanding will also allow the development of new products that, when properly used, will not produce adverse effects to man or the environment (Weber, 1972). According to the Toxic Substance Control Act (TSCA) any new or expanded-use chemical that might be released into the environment must be tested for environmental hazard.
Date: August 1985
Creator: Moses, Christopher K. (Christopher Karam)

Neuroregulation and Myosin Light Chain Phosphorylation in Ascaris Suum Obliquely Striated Skeletal Muscle

Description: Extraction and quantitation of myosin light chain two coupled with myograph recordings from Ascaris muscle perfused with calmodulin inhibitors and neurotransmitters in conjunction with their respective agonists and antagonists have been used to establish the regulation of contraction in this muscle. Densitometric tracings of isolectric focusing gels separating the regulatory light chain were used to quantitate phosphorylation in resting, contracted and flaccid muscle. These studies indicated that inhibitory neurostimulation is mediated by a true GABA receptor. Myosin-mediated contraction is responsible for maintaining the level of tension observed in resting actin-mediated muscle. Actin-mediated contraction is responsible for the rapid rise in tension following excitatory stimuli. Both systems function simultaneously and are independant.
Date: August 1985
Creator: Martin, Rex E. (Rex Edward)

Emergence, Growth, Drift and Microdistribution of Stoneflies (Plecoptera) in an Ozark Foothills Stream, Delaware County

Description: Adult stonefly emergence, nymphal growth, drift and microdistribution were examined in Battle Branch, a secondorder, spring-fed stream, from November, 1982 to May, 1984. Adults of 22 species emerged successionally, with specific adults present every month. Searching emergent objects and the stream margin was best for collection of winter and early spring emerging species. Sweeping the streamside and light trapping were most efficient for late spring and summer emerging species. Nymphal growth for nine abundant species generally fit double log or semilog models. Drift was low, but did show a post-sunset pulse. Generally, leaf material was found to be significantly related (p<O.001) to density, diversity and biomass of stoneflies in Battle Branch.
Date: May 1985
Creator: Ernst, Mark R. (Mark Richard)

Food Habits, Dietary Overlap and Electivity of Non-Game Insectivorous Fishes in an Ozark Foothills Stream

Description: Etheostoma spectabile, E. punctulatum, and Cottus carolinae were sampled Mar., 1983, - Feb., 1984, in Flint Creek, Oklahoma. Immature E. spectabile ate primarily microcrustaceans, while mature fishes relied more on mayflies and amphipods. Juvenile E. punctulatum fed upon mayflies, amphipods, and Asellus. Mature E. punctulatum ate primarily mayflies, and other relatively larger prey. Cottus carolinae consumed chironomids almost exclusively in Jan. - Feb., 1984, while mayflies were predominant the remainder of the year. No significant habitat partitioning between the two darters, and seasonal habitat segregation between C. carolinae and the two darters was found. Dietary overlap between the darters was significantly correlated (p<0.0005) to differences in x prey sizes.
Date: May 1985
Creator: Todd, C. Stan (Charles Stan)

Comparative Feeding Ecology of Leaf Pack-Inhabiting Systellognathan Stoneflies (Plecoptera) in the Upper Little Missouri River, Arkansas

Description: The feeding ecologies of leaf pack-associated systellognathan stoneflies were examined from 6 June 1980 21 May 1981. Species composition, seasonal abundance, nymphal growth, feeding habits and mouthpart morphology were determined for the eight dominant stonefly species. Prey preferences and predator-prey size relationships were also examined for omnivorous and carnivorous species. Foregut analysis from 2860 individuals indicated opportunistic feeding on the most abundant prey insects, usually in proportion to prey frequency. Feeding preference studies generally indicated random feeding on major prey groups. Prey and predator sizes were usually highly correlated (p<0.01), with predators expanding their prey size thresholds with growth. The potential for competition between sympatric stoneflies for prey is discussed.
Date: August 1983
Creator: Feminella, Jack W. (Jack William)

Effects of Aging on ACTH-Stimulated Steroidogenesis in Subcellular Fractions from Rat Adrenal Glands

Description: Young, middle-aged and old rat adrenal gland steroidogenesis was measured in isolated, superfused glands and in their subcellular fractions before and after adrenocorticotropic hormone treatment. In the latter experiment, five corticosteroids were extracted from six different subcellular fractions. Superfused glands initially produced relatively high glucocorticoid levels; thereafter, production decayed asymptotically. Steroidogenesis by young and middle-aged glands was maintained at least 1.5 to 2.5 hours before it decayed; old glands were 50% less active than younger ones and production decayed within one hour. High cholesterol and progesterone levels in certain old gland fractions were associated with correspondingly reduced 11-deoxycorticosterone and corticosterone. It is suggested that synthesis of these glucocorticoids from their accumulating precursors weakens with age.
Date: August 1982
Creator: Sawada, Tadao

Effects of Pulp and Paper Mill Effluent on Stream Primary Productivity in the Lower Sulphur River, Texas

Description: Responses of periphyton and phytoplankton productivity in the lower Sulphur River (Texas-Arkansas) to bleach-kraft mill effluent (BKME) were monitored using in situ ¹⁴C incubation. Carbon assimilation rates measured downstream of mill discharge were substantially reduced from upstream levels. Periphyton and phytoplankton chlorophyll a concentrations remained relatively unchanged by the presence of BKME. Periphyton ash-free dry weight increased near the mill outfall, but decreased further downstream. Calculated productivity efficiencies (productivity:biomass) varied with variations in ¹⁴C rates. A laboratory bioassay was designed to determine the effect of BKME light-attenuation on photosynthetic rates of upstream Sulphur River periphyton and Selenastrum capricornutum Prinz. Pooled results of bioassay runs indicated a 20 per cent BKME concentration effectively reduced control ¹⁴C-assimilation levels by 50 per cent. The downstream reduction observed for in situ productivity was 5 per cent lower than that predicted by the color bioassay.
Date: August 1982
Creator: Davis, Terrence Marvin

Population Dynamics of Macrobenthos in a Regulated Stream 1970-71 and 1978

Description: Stability of the macrobenthic community in a regulated section of the Brazos River, Texas, was evaluated. Physicochemical data and information on spatial distribution of macrobenthos were collected. Populations of two invertebrate species, Isonychia sicca and Neoperla clymene, had been greatly reduced since 1970-71 and I. sicca had been practically eliminated from this section of the Brazos. Three other insect populations, Choroterpes mexicanus, Cheumatopsche campyla and Cheumatopsyche lasia, had more than doubled their numbers since the 1970-71 study. A physicochemical gradient existed in this regulated section of the Brazos but it appeared to have changed little in comparison of earlier chemical data. A gradation of the macrobenthic community was evident as distance from the dam increased,
Date: August 1981
Creator: Coulter, James D. (James Duard)

Size Fractionation of Metabolically Active Phytoplankton and Bacteria in Two Diverse Lentic Systems

Description: Simultaneous size fractionation of plankton populations associated with NaH^14CO_3 and ^3H-glucose uptake was employed in eutrophic Lake Texoma (Texas and Oklahoma) and oligotrophic Flathead Lake (Montana). Autoradiography was utilized to determine the role of specific microorganisms in community metabolism. Ultraplankton (0.45-10 μm) dominated plankton numbers and metabolic activity in both aquatic systems. Many of the most abundant species were not the most productive, in terms of inorganic C fixation. Rates of heterotrophic uptake of ^3H-glucose were small in comparison to photolithotrophic uptake in both lakes, Photoheterotrophy was more extensive in Flathead Lake, Autoradiographs indicated that bacteria were responsible for observed photoheterotrophy. Oscillatoria sp. exhibited. mixotrophy in Lake Texoma,
Date: August 1980
Creator: Ellis, Bonnie K.