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Impacts Of Marsh Loss And Fragmentation On Microhabitat Use By Estuarine Nekton In Southwest Louisiana, John Alexander Gordon Jan 2010

Impacts Of Marsh Loss And Fragmentation On Microhabitat Use By Estuarine Nekton In Southwest Louisiana, John Alexander Gordon

LSU Master's Theses

In Louisiana, the extensive loss and fragmentation of coastal marshes has prompted inquires into the impacts these processes may have on estuarine-dependant nekton. To date, research on nekton response to marsh loss and fragmentation has been limited to landscape-level studies which focus on the relationship between nekton productivity and the availability of marsh edge. These studies have relied on the assumption that marsh edges provide the same level of support to nekton regardless of the degree of surrounding marsh loss or fragmentation. This study tested this assumption by investigating the impacts of marsh loss and fragmentation on marsh-edge characteristics and …

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Grade Level Expectations: Do They Prepare Students For Introductory College Chemistry?, Micah M. Davies Jan 2010

Grade Level Expectations: Do They Prepare Students For Introductory College Chemistry?, Micah M. Davies

LSU Master's Theses

This study investigates whether the Grade Level Expectations (GLEs) as outlined by the Louisiana Department of Education prepare students for introductory college level chemistry. A sample of 135 students in Dr. Watkins fall 2009 CHEM 1201 classes were tested for correlations between knowledge of the GLEs (chemical concept inventory pre-test and post-test score and normalized gain) and performance in CHEM 1201 (average exam score and final exam score). No significant correlations were found between any of these variables. For further analysis, students were grouped into two groups, in-state public school students and out-of-state/private school students. It was assumed that in-state …

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Development Of Stable Microencapsulated Astaxanthin Powders Using Extracted Astaxanthin From Crawfish And Shrimp Byproducts, Jianing Pu Jan 2010

Development Of Stable Microencapsulated Astaxanthin Powders Using Extracted Astaxanthin From Crawfish And Shrimp Byproducts, Jianing Pu

LSU Master's Theses

Crawfish and shrimp byproducts are an excellent source of astaxanthin. The antioxidant-rich natural astaxanthin dispersed in alpha linolenic acid-rich flaxseed oil (FO) may provide healthier functional food options for US consumers. The goals of this study were to extract astaxanthin from crawfish and shrimp byproducts and to develop astaxanthin dry powders using microencapsulation technology. Astaxanthin extracted with FO from crawfish (FOCA) and shrimp (FOSA) byproducts were stable at 30 and 40 Ž, but had substantial degradation at 50 and 60 Ž during four 4 h heating. The astaxathin degradation of FOCA and FOSA fitted with zero and first orders kinetics …

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Adoption Of Breeding Technologies In The U.S. Dairy Industry And Their Influences On Farm Profitability, Aditya Raj Khanal Jan 2010

Adoption Of Breeding Technologies In The U.S. Dairy Industry And Their Influences On Farm Profitability, Aditya Raj Khanal

LSU Master's Theses

Current trends in the U. S. dairy industry show an increase in milk cows per farm and milk production per cow, though the total number of milk cows in the industry is declining. This increase in productivity is attributed to advancements and adoption of modern dairy technologies. Breeding technologies are one of the important components of this structural change. This study analyzed the factors affecting the adoption of modern breeding technologies such as artificial insemination, embryo transplants, and sexed semen, and the impact of these technologies on farm productivity and profitability. Results of a bivariate probit model with selection showed …

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The Relationship Among Self-Efficacy, Negative Self-Statements, And Social Anxiety In Children: A Mediation, Brittany Nicole Moree Jan 2010

The Relationship Among Self-Efficacy, Negative Self-Statements, And Social Anxiety In Children: A Mediation, Brittany Nicole Moree

LSU Master's Theses

Evidence suggests that general self-efficacy, one’s beliefs about his or her global abilities, and social self-efficacy, one’s beliefs in his or her ability to navigate social situations, are strongly connected to levels of social anxiety. Negative self-statements, also known as negative self-referent cognitions, have also been linked with levels of social anxiety. Although self-efficacy and negative self-statements have been shown to be important variables in the phenomenology and maintenance of social anxiety in children, they have yet to be examined in conjunction with one another. The purpose of this study was to examine the relationship between negative self-statements and selfefficacy …

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Itraconazole Loaded Poly (Lactic-Co-Glycolic) Acid Nanoparticles For Improved Antifungal Activity, Nipur Rajan Patel Jan 2010

Itraconazole Loaded Poly (Lactic-Co-Glycolic) Acid Nanoparticles For Improved Antifungal Activity, Nipur Rajan Patel

LSU Master's Theses

PLGA (polylactic-co-glycolic acid) nanoparticles containing the hydrophobic antifungal Itraconazole (ITZ) were developed to address the need for more efficient means of treating fungal infections. PLGA-ITZ nanoparticles were synthesized using an oil-in-water emulsion evaporation method. The nanoparticles morphology (TEM), size and size distribution, zeta potential (DLS), encapsulation efficiency (UV-VIS), release profile, and antifungal activity were characterized. The blank NPs and loaded PLGA-ITZ NPs were spherical with diameters of 201±5 nm, 232±1 nm and 223±36 nm at 0%, 12.5% and 25% loadings, respectively. All synthesized particles measured a negative zeta potential ranging from -28 to -33 mV. The maximum encapsulation efficiency of …

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The Effectiveness Of A Natural Carbohydrate Source (Sun-Dried Raisins) Versus Sports Jelly Beans On Prolonged Cycling Performance, Helena Rietschier Jan 2010

The Effectiveness Of A Natural Carbohydrate Source (Sun-Dried Raisins) Versus Sports Jelly Beans On Prolonged Cycling Performance, Helena Rietschier

LSU Master's Theses

PURPOSE: This study was designed to examine the effects of sun-dried raisins versus sports jellybeans on endurance performance in trained cyclists/triathletes. METHODS: Ten healthy males (18-33 y) completed one water-only acclimatization (WAT) exercise trial and two randomized exercise trials. Each trial consisted of a 120-minute constant intensity glycogen depletion period followed by a 10-km time trial (TT). During each experimental trial, participants consumed isocaloric amounts of sun-dried raisins (SDR) or Sports Jelly Beans(SJB) in 20-minute intervals. Measurements included: time to complete 10-km TT, power output during 10-km TT, blood glucose levels and respiratory exchange ratio (RER) during glycogen depletion period, …

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Status Of Wintering Grassland Birds In A Post-Hurricane, Salvage-Logged Forest, Matthew Edward Brooks Jan 2010

Status Of Wintering Grassland Birds In A Post-Hurricane, Salvage-Logged Forest, Matthew Edward Brooks

LSU Master's Theses

North American grassland birds have been declining at an alarming rate. Winter habitat for grassland species in the southeastern U.S. generally occurs within forests subject to management. I studied wintering grassland bird communities in De Soto National Forest in southern Mississippi. My objectives were to: 1) Assess bird communities and vegetation structure in upland forest stands that were salvage-logged following Hurricane Katrina, in stands managed for Red-cockaded Woodpeckers (Picoides borealis, RCW), and in stands containing bogs; and 2) Determine the extent of the association between vegetation and occurrence of the common wintering grassland birds. I conducted bird and vegetation surveys …

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"To Liberate Communication": The Realist And Paul Krassner's 1960s, Terry Joel Wagner Jan 2010

"To Liberate Communication": The Realist And Paul Krassner's 1960s, Terry Joel Wagner

LSU Master's Theses

Paul Krassner began publishing a small-circulation magazine called The Realist in New York City in 1958 because he believed there existed excessive restraints on speech in American culture. The publication began with a combination of earnest critiques and good-humored satires on such topics as organized religion, sexual mores, Cold War paranoia, and civil rights. By the mid-sixties, the magazine was enlarging the space not just for what opinions could be expressed but also for the way those opinions were expressed and, in the process, testing the boundaries of obscenity. As Krassner became a bitter opponent of the Vietnam War and …

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The Influence Of Two Estrogens On The Sex And Ovarian Development Of Eastern Oysters (Crassostrea Virginica) Maintained In A Closed Recirculating System, Wesley Michael Burnside Jan 2010

The Influence Of Two Estrogens On The Sex And Ovarian Development Of Eastern Oysters (Crassostrea Virginica) Maintained In A Closed Recirculating System, Wesley Michael Burnside

LSU Master's Theses

As a multi-million dollar industry, production of the eastern oyster Crassostrea virginica is significant to the economy of the nation’s coastal regions. The cost of commercial oyster aquaculture has higher inputs than the oyster fishery, but larger, better quality oysters can be produced for culture by the stable availability of triploid individuals.

The goal of this project was to determine if the use of an estrogen, estradiol-17β or estradiol-3-benzoate, at a consistent environmental temperature would increase the percentage of females in a population, as well as ovarian development of eastern oysters. Ultimately, this could be applied to triploids to increase …

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The Effects Of Channel Stability On Benthic Macroinvertebrates In Southeastern Louisiana Streams, Peter Markos Jan 2010

The Effects Of Channel Stability On Benthic Macroinvertebrates In Southeastern Louisiana Streams, Peter Markos

LSU Master's Theses

Water chemistry, habitat quality, and channel stability interact to influence a stream’s biological integrity. The goal of this project was to assess how channel stability, together with other physicochemical stream measurements, are associated with the structure and abundance of resident macroinvertebrate communities. I recorded multiple physicochemical parameters and calculated a Pfankuch habitat stability index monthly for a year at potential reference streams in southeastern Louisiana. I assessed the relationships of channels stability with measured physicochemical parameters with multiple regression and principle components analysis. Mixed model multivariate analysis of variance was used to determine associations of habitat characteristics with resident macroinvertebrate …

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Characterization Of Composite Piezoelectric Materials For Smart Joint Applications, Hari Prasad Konka Jan 2010

Characterization Of Composite Piezoelectric Materials For Smart Joint Applications, Hari Prasad Konka

LSU Master's Theses

Piezoelectric materials have the ability to provide desired transformation from mechanical to electrical energy and vice versa. When a mechanical force is applied to the piezoelectric material an electrical voltage is generated and when an electrical voltage is applied to the piezoelectric material it gets strained or deformed. Owing to these characteristics piezoelectric materials can be used as a sensor, an actuator, as well as a power generation unit. The high brittleness property of the original piezoelectric material is one of the major constraints in using them in the engineering applications. In order to overcome this disadvantage the composite piezoelectric …

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Branding The Bear, Veni Harlan Jan 2010

Branding The Bear, Veni Harlan

LSU Master's Theses

Harlan, Veni S, B.F.A., Louisiana State University, 1981 Master of Fine Arts, Fall Commencement, 2010 Major: Graphic Design Branding the Bear Dissertation directed by Professor Rod Parker Pages in dissertation, 64. Words in abstract, 350. ABSTRACT Currently due to successful restoration efforts, the Louisiana Black Bear sub-species is rebounding. Correspondingly this increase in numbers accompanies the rise of human-bear conflict. Fiction, misinformation, resentment, and devaluation of the bear as a valuable asset stand to undermine the tremendous strides made by multiple public and private agencies over the course of twenty years. Discovery revealed a lack of knowledge by the public …

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Functional Characterization Of A Non-Cytoplasmically Localized Dps Protein From Deinococcus Radiodurans, Brian Reon Jan 2010

Functional Characterization Of A Non-Cytoplasmically Localized Dps Protein From Deinococcus Radiodurans, Brian Reon

LSU Master's Theses

The gram-positive eubacterium Deinococcus radiodurans is widely recognized for its extreme resistance to various DNA-damaging conditions, such as desiccation and ionizing and ultraviolet radiation. D. radiodurans is one of only a few bacteria which encode two Dps (DNA protection during starvation) proteins. Here I report the cloning and purification of a more soluble Dps2, Ntrunc. Also, the initial characterization of a truncated Dps2, which lacks the C-terminal metal binding loop, shows that this region is important for proper oligomerization. Furthermore, Dps2 expression was found to be moderately induced when stressed with exogenous H2O2, and expression levels were not altered by …

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Age Related Productivity And Consistency Of Nest Initiation Timing Of Wild Mallards In Eastern North Dakota, Timothy Charles Kimmel Jan 2010

Age Related Productivity And Consistency Of Nest Initiation Timing Of Wild Mallards In Eastern North Dakota, Timothy Charles Kimmel

LSU Master's Theses

Mallards Anas platyrhnchos are arguably the most researched waterfowl species in North America. They exhibit great flexibility in certain breeding metrics such as timing of nest initiation and clutch size. A study on captive female Mallards (Batt and Prince 1979) fed ad libitum, held in identical breeding compartments, and paired with the same mate in each year of the study exhibited substantial variation in the timing of nest initiation within a given year, yet some individual females demonstrated consistency in initiation date among years. My objective was to examine breeding metrics such as timing of nest initiation and clutch size …

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Laser-Assisted Zona Pellucida Hatching Of Frozen-Thawed In Vivo-Produced Bovine Embryos, Mindy Kaye Chiasson Jan 2010

Laser-Assisted Zona Pellucida Hatching Of Frozen-Thawed In Vivo-Produced Bovine Embryos, Mindy Kaye Chiasson

LSU Master's Theses

Incomplete zona hatching or failure of the zona to rupture compromises post-transfer embryo viability and conceptus development. Assisted hatching prior to the transfer of frozen-thawed bovine embryos has been proposed as a means to increase recipient pregnancy rates. The objective of this study was to determine if laser-assisted hatching would improve in vivo-produced frozen-thawed bovine embryo hatching and pregnancy rates. In Experiment I,II and III frozen direct-transfer embryos received either two a or three symmetrical rents at either 40% or 80% through the outer zona surface using the Hamilton Thorne XYClone® (Hamilton Thorne Biosciences) diode laser at 90% power with …

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Investigating The Effectiveness Of Informal Science Education Through Quantitative And Qualitative Analysis: Ocean Commotion, Catherine Angela Sutera Jan 2010

Investigating The Effectiveness Of Informal Science Education Through Quantitative And Qualitative Analysis: Ocean Commotion, Catherine Angela Sutera

LSU Master's Theses

Informal science education serves as an important source for science education for both individuals and school groups. However, the effectiveness of school visits to informal science education events outside of either museums or science centers has received little investigation. This study explores the short-term effects of a hands-on learning experience on students’ attitude and content knowledge. Specifically, it investigates the impact of Ocean Commotion, a one-day event where exhibitors present information and hands-on demonstrations about marine environments and products, especially those important to Louisiana. Pre-tests were utilized to document students’ initial knowledge of and attitude toward wetlands and the ocean, …

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A High Fat Diet Attenuates The Fermentation Effects Of Resistant Starches And Fructans, Felicia Robin Goldsmith Jan 2010

A High Fat Diet Attenuates The Fermentation Effects Of Resistant Starches And Fructans, Felicia Robin Goldsmith

LSU Master's Theses

In our previous studies, ingestion of prebiotics in low fat diets resulted in decreased cecal pH from 8 to about 6 and increases in short chain fatty acids indicating robust fermentation. However, in some preliminary studies this effect on fermentation was not seen when rodents were obese and/or fed a high-fat diet. This comprehensive high-fat diet study was conducted to determine which sources and combinations of prebiotics would enhance fermentation despite a high dietary fat content. The effects of prebiotics in a high-fat diet (44% energy) on pH, cecal weights, abdominal fat, and body weight were studied in mature male …

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Altruism And Alcohol Dependence: Is There A Relationship Between Helping Others And Recovery?, Alan Nicholson Jan 2010

Altruism And Alcohol Dependence: Is There A Relationship Between Helping Others And Recovery?, Alan Nicholson

LSU Master's Theses

Alcoholics Anonymous (AA) and the Twelve Steps have been instrumental in the recovery of numerous persons who are alcohol dependent. Altruism has been found to have a positive effect on physical and psychological functioning in diverse populations. A key component of AA is altruistic helping and service to others to recover from alcohol dependency. The current study explores the relationship between altruism and recovery from alcohol dependency. Self-report survey data focusing on altruism, AA altruistic activities, and recovery from alcohol dependence was collected from 92 AA members and analyzed to assess for correlations between altruism and recovery. No statistically significant …

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Stochastic Trends In Crop Yield Density Estimation, David I. Maradiaga Jan 2010

Stochastic Trends In Crop Yield Density Estimation, David I. Maradiaga

LSU Master's Theses

The search for improved methods of estimating crop yield density functions has been a theme of recurrent research interest in agricultural economics. Crop yield density functions are the statistical instrument that generates probability estimates of yield risk, and risk is an important decision variable in production agriculture. Recent research in crop yield density estimation suggests that yield probability estimates can be sensitive to the way yield data are filtered, and if true, then the search for an “adequate filter” is warranted. Such a quest is pursued in this study. It is proposed that unit-root tests can be used to identify …

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The Model System C. Elegans Demonstrates The Health Benefits Of Legumes And The Potential Benefits Of Legume Consumption, Carla Michele Sandlin Jan 2010

The Model System C. Elegans Demonstrates The Health Benefits Of Legumes And The Potential Benefits Of Legume Consumption, Carla Michele Sandlin

LSU Master's Theses

Legumes are high in protein and are a good source of fiber and folate. They contain beneficial oligosaccharides, plant sterols and phenolics. The purpose of this study was to demonstrate the health benefits of legumes using the model system Caenorhabditis elegans (C. elegans). Nine legumes (black beans, cranberry beans, dark red beans, great northern beans, large lima beans, lentils, light red kidney beans, navy beans and white kidney beans) were tested in the C. elegans model system. The various legume samples were ground using a centrifugal mill to 0.75mm, suspended in water (1% w/v) solution and autoclaved. C. elegans were …

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Patterns Of Habitat Suitability And Abundance Trends Of Current And Candidate Coastal Fish Species Of Concern In Louisiana, Elin Rose Sandy Jan 2010

Patterns Of Habitat Suitability And Abundance Trends Of Current And Candidate Coastal Fish Species Of Concern In Louisiana, Elin Rose Sandy

LSU Master's Theses

Louisiana’s estuaries and coastal waters play an important role in providing habitat for several estuarine-dependent species and also serve as a nursery for the juveniles of several other species. The current rate of land loss in Louisiana and the decline of estuarine-dependent species force us to improve our understanding of the recruitment of these species into Louisiana’s estuaries. Habitat suitabilities were developed for several fish species of concern (SOC) and other estuarine-dependent species across three environmental gradients, abundance patterns were developed for seasons, five-year intervals, and coastal study areas (CSAs). Chi-square analyses and ANOVAs were then used to test for …

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Misconceptions On Force And Gravity Among High School Students, Jane Ragasa Pablico Jan 2010

Misconceptions On Force And Gravity Among High School Students, Jane Ragasa Pablico

LSU Master's Theses

The goal of this study is to determine prevalent or dominant misconceptions on force and gravity among high school students. A survey instrument consisting of 12 qualitative questions requiring both answers and written explanations was used to gather students’ ideas and beliefs in situations involving force and gravity. Furthermore, it examined whether the proportion of students having misconceptions per question are correlated with gender and the type of school Physics background. The results show that the respondents have misconceptions that are similar to the misconceptions found in previous research. The number of misconceptions and the proportion of students having misconceptions …

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Assessing The Suitability Of Coagulation Pretreatment On Poultry Processing Wastewater For Optimized Dissolved Air Flotation, Adam James Dassey Jan 2010

Assessing The Suitability Of Coagulation Pretreatment On Poultry Processing Wastewater For Optimized Dissolved Air Flotation, Adam James Dassey

LSU Master's Theses

Eleven metal coagulants and one polyelectrolyte were assessed on their suitability for assisting a dissolved air flotation (DAF) system in treating poultry processing wastewater. The DAF unit was designed to maximize the microbubble production by varying the pressure, temperature, hydraulic retention time, and air flow parameters. The maximum microbubble flow from the designed system produced 30 mL of air per L of water. This value was considered low compared to other systems, but attempts to increase the microbubble volume in the current system beyond this value resulted in the coalescing of microbubbles due to turbulent conditions. Jar tests were used …

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Effects Of Varying Levels Of Cottonseed Hulls On Growth And Metabolic Indications Of Rumen Development Of Dairy Calves, Ryan Doescher Jan 2010

Effects Of Varying Levels Of Cottonseed Hulls On Growth And Metabolic Indications Of Rumen Development Of Dairy Calves, Ryan Doescher

LSU Master's Theses

A study was conducted to determine the effects of varying levels of cottonseed hulls on growth and metabolic indications of rumen development of dairy calves. Sixty-four Holstein calves (Heifers, n=40; Bulls, n=24) were randomly assigned to one of four dietary treatments which included calf starters containing no cottonseed hulls (control; C), 10% cottonseed hulls (10% CSH), 15% cottonseed hulls (15% CSH), or 20% cottonseed hulls (20% CSH). Calves were fed their respective treatments beginning on day 6 until day 56 of age. Body weights were measured at birth and biweekly thereafter until day 56 of age. Wither and hip heights …

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Play It Loud: Hip Hop In The Language Arts Classroom, B Cord Mckeithen Jan 2010

Play It Loud: Hip Hop In The Language Arts Classroom, B Cord Mckeithen

LSU Master's Theses

Hip-hop music and its place in education has been thoroughly researched over the last two decades by many scholars and educators from all over the world. This research paper discusses hip-hop’s merit in the classroom, building upon prior research from books and journal articles, along with my own research that I conducted with students at a southern Louisiana high school. Educators in the field of language arts must find new methods when it comes to teaching our youth and leave behind many of the traditional ways that previous generations were accustomed to. The idea of hip-hop in education, in this …

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In Sickness And In Health: Experiencing Medical Spaces In Mbarara (Uganda), Kara E. Miller Jan 2010

In Sickness And In Health: Experiencing Medical Spaces In Mbarara (Uganda), Kara E. Miller

LSU Master's Theses

This thesis is a contribution to cross-cultural studies on health and medicine explored through the material and symbolic facets of health care in a region of Southwest Uganda. Research conducted in the healing spaces of Mbarara reflects traditions in the anthropology of the body and brings a lived perspective to conditions of sickness and wellness. By tracing the biographies of treatment spaces, the medical landscape is evaluated in terms of participants’ perceptions, convictions, and knowledge sets. Phenomenological methodology is employed in this exploration of ill states and curative places, which braids concepts and academic work in the areas of medicine, …

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Taphonomy And Sedimentology Of Two Miocene Vertebrate Fossil Sites On Fort Polk, Louisiana, Julie Lynn Hill Jan 2010

Taphonomy And Sedimentology Of Two Miocene Vertebrate Fossil Sites On Fort Polk, Louisiana, Julie Lynn Hill

LSU Master's Theses

The discovery of a terrestrial mammalian fauna in the Miocene deposits on Fort Polk, Louisiana, fills a geographic gap in the Gulf Coast paleontological framework, but the provenance of the fossils, nature of the depositional environments, and relationships between the sites is still debated. This is especially true for the TVOR site cluster. TVOR SE has a mixture of marine and terrestrial vertebrates in association with a partly dissolved, in situ bed of articulated oyster shells, which stands in contrast to the fully terrestrial and freshwater assemblage at TVOR, and the indeterminate site TVOR S. Although limited outcrop may bias …

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A Study Of Passalid Beetle Prokaryote And Yeast Gut Symbionts, Stephanie Rachelle Gross Jan 2010

A Study Of Passalid Beetle Prokaryote And Yeast Gut Symbionts, Stephanie Rachelle Gross

LSU Master's Theses

Scheffersomyces stipitis (=Pichia stipitis) is a xylose-fermenting and assimilating yeast (Ascomycota: Saccharomycotina) consistently isolated from the gut of Odontotaenius disjunctus (Coleoptera: Passalidae). This filamentous yeast is often attached to the wall of the posterior hindgut of the beetle by a holdfast. Gallery walls of white-rotted wood inhabited by the beetle are lined with macerated wood and frass that includes the yeast and other microbes. Previous studies have mentioned the relationship between the passalid and this yeast; however, passalid beetles also harbor a community of prokaryotes in their guts that have not been characterized. Experiments using culturing and cloning techniques and …

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Dopaminergic Input To The Equine Pituitary: Seasonal And Estradiol Effects, Sarah Case Clavier Jan 2010

Dopaminergic Input To The Equine Pituitary: Seasonal And Estradiol Effects, Sarah Case Clavier

LSU Master's Theses

Two experiments were conducted to study the effects of season and estradiol administration on dopaminergic input to the equine adenohypophysis. Experiment 1 began in the spring with 8 mares and 8 stallions and was repeated again in the summer, fall, and winter. Horses were given sulpiride injections of eight incremental doses (0.25 to 32 µg/kg BW). Within each group of 8 horses, half received the sulpiride in an increasing manner, the other half in a decreasing manner. Prolactin concentrations peaked in the first 15 to 30 min in all horses in all seasons. Prolactin areas under the curve increased (P < 0.001) with increasing doses of sulpiride, and were highest (P < 0.05) in March for stallions, but in June for mares. The calculated half-maximum values, which should be proportional to the dopaminergic input to the pituitary, were lowest (P < 0.05) in June and greatest in September. The variation in half-maximum values with season indicated a change in dopaminergic input to the pituitary, with lowest input occurring in June in both sexes. Experiment 2 was designed to determine if the degree of dopaminergic input to the adenohypophysis is altered by estradiol administration. Twelve geldings were used. On day 0, geldings received an i.m. injection of either estradiol cypionate (ECP; n = 6) or vegetable oil (n = 6) at one of two dose volumes (2 vs. 10 mL). On day 6, all geldings received an injection of sulpiride at 0.082 µg/kg BW in saline. Sulpiride injections were repeated every other day with the dose increasing each day, from 0.164 to 100 µg/kg BW. Estradiol pretreatment increased (P < 0.05) the prolactin response to sulpiride at the 2.56 µg/kg dose and higher. However, the half-maximum values for ECP-treated and control geldings did not differ, indicating that the amount of sulpiride needed to counterbalance the amount of dopamine reaching the pituitary was unaltered by estradiol treatment. It was concluded that estradiol likely stimulates prolactin production and secretion after sulpiride directly at the lactotrope level, rather than by decreasing hypothalamic dopamine input to the lactotropes.

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