A large river system typically derives the majority of its biomass from production within the floodplain. The Neches River in the Big Thicket National Preserve is a large blackwater river that has an extensive forested floodplain. Organic carbon was analyzed within the floodplain waters and the river (upstream and downstream of the floodplain) to determine the amount of organic carbon from the floodplain that is contributing to the nutrient dynamics in the river. Dissolved organic carbon was significantly higher at downstream river locations during high discharge. Higher organic carbon levels in the floodplain contributed to increases in organic carbon within the Neches River downstream of the floodplain when Neches River discharges exceeded 10,000 cfs. Hurricane Rita passed through the Big Thicket National Preserve in September 2005. Dissolved organic carbon concentrations recorded after Hurricane Rita in the Neches River downstream of the floodplain were significantly higher than upstream of the floodplain. Dissolved organic carbon was twice as high after the hurricane than levels prior to the hurricane, with floodplain concentrations exceeding 50 ppm C. The increase in organic carbon was likely due to nutrients leached from leaves, which were swept from the floodplain trees prior to normal abscission in the fall. …

Triclosan (TCS) and triclocarban (TCC), widely used antimicrobial agents found in numerous consumer products, are incompletely removed by wastewater treatment plant (WWTP) processing. Methyl-triclosan (M-TCS) is a more lipophilic metabolite of its parent compound, TCS. The focus of this study was to quantify bioaccumulation factors (BAFs) for TCS, M-TCS, and TCC in Pecan creek, the receiving stream for the City of Denton, Texas WWTP by using field samples mostly composed of the alga Cladophora sp. and the caged snail Helisoma trivolvis as test species. Additionally, TCS effects on E. coli and Arabidopsis have been shown to reduce fatty acid biosynthesis and total lipid content by inhibiting the trans-2 enoyl- ACP reductase. The lipid synthesis pathway effects of TCS on field samples of Cladophora spp. were also investigated in this study by using [2-14C]acetate radiolabeling procedures. Preliminary results indicate high TCS concentrations are toxic to lipid biosynthesis and reduce [2-14C]acetate incorporation into total lipids. These results have led to the concern that chronic exposure of algae in receiving streams to environmentally relevant TCS concentrations might affect their nutrient value. If consumer growth is limited, trophic cascade strength may be affected and serve to limit population growth and reproduction of herbivores in …

Murine neuronal networks, derived from embryonic frontal cortex (FC) tissue grown on microelectrode arrays, were used to investigate zinc toxicity at concentrations ranging from 20 to 2000 mM total zinc acetate added to the culture medium. Continual multi-channel recording of spontaneous action potential generation allowed a quantitative analysis of the temporal evolution of network spike activity generation at specific zinc acetate concentrations. Cultures responded with immediate concentration-dependent excitation lasting from 5 to 50 min, consisting of increased spiking and enhanced, coordinated bursting. This was followed by irreversible activity decay. The time to 50% and 90% activity loss was concentration dependent, highly reproducible, and formed linear functions in log-log plots. Network activity loss generally preceded morphological changes. 20% cell swelling was correlated with 50% activity loss. Cultures pretreated with the GABAA receptor antagonists bicuculline (40 mM) and picrotoxin (1 mM) lacked the initial excitation phase. This suggests that zinc-induced excitation may be mediated by interfering with GABA inhibition. Partial network protection was achieved by stopping spontaneous activity with either tetrodotoxin (200 nM) or lidocaine (250 mM). However, recovery was not complete and slow deterioration of network activity continued over 6 hrs. Removal of zinc by early medium changes showed irreversible, catastrophic …

In order to understand the structural changes in myosin S1, fluorescence polarization and computational dynamics simulations were used. Dynamics simulations on the S1 motor domain indicated that significant flexibility was present throughout the molecular model. The constrained opening versus closing of the 50 kDa cleft appeared to induce opposite directions of movement in the lever arm. A sequence called the "strut" which traverses the 50 kDa cleft and may play an important role in positioning the actomyosin binding interface during actin binding is thought to be intimately linked to distant structural changes in the myosin's nucleotide cleft and neck regions. To study the dynamics of the strut region, a method of fluorescent labeling of the strut was discovered using the dye CY3. CY3 served as a hydrophobic tag for purification by hydrophobic interaction chromatography which enabled the separation of labeled and unlabeled species of S1 including a fraction labeled specifically at the strut sequence. The high specificity of labeling was verified by proteolytic digestions, gel electrophoresis, and mass spectroscopy. Analysis of the labeled S1 by collisional quenching, fluorescence polarization, and actin-activated ATPase activity were consistent with predictions from structural models of the probe's location. Although the fluorescent intensity of the …

The expression of two cotton osmotin genes was evaluated in terms of the mRNA and protein expression patterns in response to chemical inducers such as ethylene, hydrogen peroxide, and sodium chloride. Reverse transcriptase-polymerase chain reactions (RT-PCR) indicated that osmotin mRNAs are expressed constitutively in root tissues of cotton plants, and that they are rapidly induced in leaf and stem tissues upon ethylene treatment. Real time RT-PCR indicated that osmotin transcript levels were induced 2 to 4 h after treatment with ethephon. The osmotin mRNA levels appear to increase 12 h after treatment, decrease, and then increase again. The osmotin protein expression patterns were analyzed in Western blot analyses using an anti-osmotin antibody preparation. A 24-KDa protein band was detected from cotton plants treated with the inducers. The 24-KDa osmotin proteins were induced 4 h after treatment with ethephon, while down-regulated 96 h after treatment. Multiple osmotin isoforms were observed to be induced in cotton plants upon treatment with ethephon by two-dimensional gel electrophoresis. One goal of this dissertation research was to genetically engineer two cotton osmotin genes to routinely overproduce their antifungal proteins in transgenic Arabidopsis and cotton plants as a natural defense against fungal infections, using co-cultivation with Agrobacterium …

Lewisville Lake Environmental Learning Area (LLELA) is an 809-hectare property in Denton County, TX. A study of the vegetation community identified 466 species in 104 families, with 25% of the species from only two families, Asteraceae and Poaceae. The property demonstrates the characteristics of an early successional community, dominated by weedy species. Prairie communities are dominated by Johnson grass and ragweed, with climax tall grass prairie communities only in areas that have been planted with native grass seed. Forest communities are similarly in an early successional stage, dominated by the hackberry-elm-ash alliance, with small remnants of native Cross Timbers found in isolated patches. Species richness and diversity were highest in the forests and lowest in the wetlands; evenness, though not different across ecosystems, demonstrated a strong seasonal component. The species list was compared with previously reported lists for Denton County, and 256 species identified had not been previously reported for the county. A wetland restoration study was conducted to determine if there was a difference in survival and growth between potted transplants with intact root systems and bare-root transplants. Two different mesh sizes were used for protection, and the success of the different caging was evaluated. Of eight species, only …

Established interspecific metabolic allometric relationships do not adequately describe the complexity and variable physiological states of developing animals. Consequently, intraspecific allometric relationships of oxygen consumption and carbon dioxide production as a function of body mass; the respiratory quotient; the function of the silk cocoon; and body composition were investigated for each distinct developmental stage of the silkworm, Bombyx mori. Whole animal O2 consumption in Bombyx ranged from 0.00064 + 0.000047 ml O2 .hr-1 at larval instar I to 0.77 + 0.06 ml O2 .hr-1 in pre-pupal, falling to 0.21+ 0.01 ml O2 .hr-1 in the pupae. Those instars having a significant relationship between O2 consumption as a function of body mass, the slope of the line relating O2 consumption to body mass varied between 0.99 and 1.02, while across all instars the slope was 0.82. Developmental allometry should be presented for individual developmental stages because the individual allometric exponents of the stages can be significantly different from the overall allometric exponent throughout development and in some cases, the overall allometric exponent can be a statistical artifact. The first larval instar of Bombyx mori has the lowest cross sectional area of high metabolic tissue of the midgut (27%) and had one …

The black-tailed prairie dog (Cynomys ludovicianus) has experienced dramatic declines over much of its historical range due to habitat loss, plague, poisonings, and shootings. Many populations now occur as isolated genetic relicts. A multiple locus genetic profile was obtained using microsatellite analyses of six polymorphic nucleotide repeats from 319 black-tailed prairie dogs collected from 16 colonies throughout the state of Texas. This assessment revealed that existing populations have sufficient variation at all six loci to verify the usefulness of this approach as a primary genetic tool in conservation and preservation. The data reveals regional-dependent frequency patterns as well as support for founder/bottleneck effects for several of the 16 sites. Although the prairie dog population in Texas as a whole may appear genetically diverse, considerable genetic divergence has already occurred among the subpopulations (FST = 0.164). Isolation by distance is supported by genic differentiation analysis (P < 0.001) and pairwise correlation analysis between genetic distance and geographic distance (P < 0.001). Prairie dogs from six (COC, LUBA, LUBC, LUBD, LUBE, and TAR) of the original 16 sites have been relocated or exterminated, or were in the process of being relocated. Results indicated the following colonies (COT, DAL, HOW, and HUD) are …

Archaeological and paleontological datasets are used in conservation to add time-depth to ecology. In central Texas several top carnivores including prehistoric Native American hunters have been extirpated or have had their historic ranges restricted, which has resulted in pest-level white-tailed deer (Odocoileus virginianus texana) populations in some areas. Predator extermination has dramatically reduced the average body size of members of the extant predator guild, and large carnivores most capable of hunting white-tailed deer are extirpated. Character release in the remaining “large” predatorsmesocarnivoresis a predicted outcome related to the adaptive vacuum at the top of the trophic hierarchy. Differences in body size of deer between prehistory and modernity are expected given that a lack of predation likely has increased intraspecific competition for forage among deer resulting in smaller body size today. In fact modern deer from settings without harvest pressure are significantly smaller than those from harvested areas and from prehistoric deer. From a natural history perspective, this research highlights potential evolutionary causes and effects of top-predator removal on deer populations and related components of biological communities in central Texas.