Biology Commons^™

Investigating The Initial Detection Stage Of Meiotic Silencing By Unpaired Dna In The Model Organism Neurospora Crassa, Pegan A. Sauls

Theses and Dissertations

In an attempt to neutralize transposable elements or retrovirus invasions Neurospora crassa will rely on one of its many genome defense mechanism, Meiotic Silencing by Unpaired DNA (MSUD). MSUD works in a two-step process that first detects unpaired sequences between homologous chromosomes followed by downstream silenced expression of the sequence. The ultimate silencing stage of MSUD is widely accepted to operate through an RNAi-like system. However, the mechanics of the detection step of MSUD remains elusive. The research presented attempts to elaborate on how the initial stage of MSUD occurs and its specifics. First, a genetic approach is utilized to …

Hatching Asynchrony In European Starlings ( Sturnus Vulgaris ), Jason Hanser

Theses and Dissertations

Across a wide range of avian taxa, eggs within clutches hatch asynchronously, placing later hatched nestlings at a disadvantage. Here, we explore the proximate and ultimate causes of hatching asynchrony within European starlings, Sturnus vulgaris. Specifically, we investigate the effect of ambient temperature on egg viability and incubation behavior prior to clutch completion. Additionally, we examine the potential for storage time and maternally-deposited yolk testosterone to influence rates of embryonic development and hatching patterns within European starlings.

Evolution And Biogeography Of Mesoamerican Small Mammals: With Focus On The Genus Handleyomys And Related Taxa, Ana Villalba Almendra

Theses and Dissertations

Mesoamerica is considered a biodiversity hot spot with levels of endemism and species diversity likely underestimated. For mammals, the patterns of diversification of Mesoamerican taxa still are controversial. Reasons for this include the region's complex geologic history, and the relatively recent timing of such geological events. Previous studies, however, support the view that substantial migration between North (NA) and South America (SA) occurred prior or/and during the Great American Biotic Interchange (GABI) ~3.5 Ma. This was followed by repeated periods of isolation during Pleistocene climatic oscillations, which produced most of the diversification in the region. From a North American origin, …

Single-Walled Carbon Nanotube And Graphene: Nano-Delivery Of Gambogic Acid Increases Its Cytotoxicty In Various Cancer Cells, Lamya A. M Saeed

Theses and Dissertations

Nanomedicine is a new branch of medicine that has been developed due to the critical need to treat challenging diseases, especially cancer since it remains a significant cause of morbidity and mortality worldwide and the second most common cause of death after heart disease in the USA. One of the most important health care applications of nanomedicine concerns the development of drug delivery systems. Graphene (Gn), an atom-thick carbon monolayer of sp2- bonded carbon atoms arranged in a two dimensional (2D) honeycomb crystal lattice, and single-walled carbon nanotubes (SWCNTs) (1D, tubular) are among the most promising nanomaterials with the capability …

Seta Structure In Members Of The Coleochaetales ( Streptophyta ), Timothy Richard Rockwell

Theses and Dissertations

The charophycean green algae, which include the Coleochaetales, together with land plants form a monophyletic group, the streptophytes. The order Coleochaetales, a possible sister taxon to land plants, is defined by its distinguishing setae (hairs), which are encompassed by a collar. Previous studies of these setae yielded conflicting results and were confined to one species, Coleochaet. scutata. In order to interpret these results and learn about the evolution of this character, setae of four species of Coleochaete and the genus Chaetosphaeridium within the Coleochaetales were studied to determine whether cellulose, callose, and phenolic compounds contribute to the chemical composition of …

In Vivo Modulation Of Rhythmically Active Neural Networks In The Crustacean Stomatogastric Ganglion, Alexandra Mead Yarger

Theses and Dissertations

Rhythmic motor patterns are found throughout all living organisms and are responsible for maintaining some of our most fundamental behaviors. The motor circuits producing these behaviors are flexible and able to adapt to changing internal and environmental conditions, yet stable enough to maintain function within certain boundaries. Central pattern generators (CPGs), which are the primary source of this stability, reliably maintain activity patterns and thus the behaviors they drive. The crab stomatogastric nervous system contains the well-characterized gastric mill (chewing) and pyloric (filtering of food) CPGs. In vitro, the pyloric rhythm is stereotyped with little variation over time. Temperature, inter-circuit …

Environmental Impacts On Life History In Container Breeding Mosquitoes, Kathleen May Westby

Theses and Dissertations

In this dissertation I explore different ways that the environment impacts life history in mosquitoes in ways that may alter vectorial capacity. In chapter I, I tested if short-term sugar deprivation experienced after exposure to La Crosse virus altered infection rates in Aedes albopictus and if sugar treatment and virus infection status altered blood feeding behavior and fecundity. I found no evidence that sugar deprivation impacted infection rates or fecundity. Sugar deprivation did increase blood feeding. There was no effect of infection status on blood feeding or fecundity. In chapter II, I tested for effects of seasonal cues (temperature and …

Exploring The Antibacterial, Antioxidant, And Anticancerproperties Of Lichen Metabolites, Gajendra Shrestha

Theses and Dissertations

Natural products have been a significant source of new drugs, especially in treating cancer, infectious diseases, hypertension, and neurological disorders. Although many natural metabolites have been screened and yielded pharmaceutically important drugs, many potential sources of natural product drug therapies still need to be investigated, including lichens. Lichens are symbiotic systems consisting of a filamentous fungus and a photosynthetic partner (an eukaryotic alga and/or cyanobacterium). Lichens produce an impressive variety of unique secondary compounds and have been used as ingredients in folk medicines for centuries. Demonstrated biological roles based on lichen chemistry include: antibiotics, anti-proliferative, antioxidants, anti-HIV, anti-cancer, immunomodulation, and …

Rab Proteins And Alzheimer's: A Current Review Of Their Involvement In Amyloid Beta Generation With Focus On Rab10 Expression In N2a-695 Cells, Ivan Arano Rodriguez

Theses and Dissertations

This thesis work describes the role of Rab proteins in amyloid processing and clearance in different cell pathways. It also describes an experimental approach used to analyze the expression effects of Rab10 in amyloid beta production. Since the main theory behind neurodegeneration in Alzheimer's disease claims that high levels of amyloid beta 42 (Aβ42) molecules trigger widespread neuronal death, control of Aβ42 has been a main target in Alzheimer's disease research. In addition, several studies show increased levels of particular Rab proteins in Alzheimer's pathogenesis. However, no review consolidates current findings in neurodegeneration of Alzheimer's with Rab protein dysfunction. The …

Spiders Or Butterflies? Despite Student Preference, Gender-Biased Lesson Models Do Not Impact Interest, Attitude, And Learning In Biology, Amy N. Buxton

Theses and Dissertations

Educational research often emphasizes the prevalent gender gap between males and females in science, technology, engineering, and mathematics (STEM) fields. While many studies have found a gender bias when it comes to specific areas of science, little has been done to analyze the effects of how we teach within each of these subjects. In our study, we took a new angle on gender research by specifically considering whether there is a gender gap in how the models (the specific lesson examples/content used to teach a broader biology topic) used to teach biology affect student interest, attitude, and learning. We first …

Latitudinal Variation In Lifetime Survival And Reproduction In A Burying Beetle, Clinton T. Laidlaw

Theses and Dissertations

Temperature variation experienced across a latitudinal range is tied to changes in lifespan and life history across multiple taxa. Two patterns of adaptation to latitudinal temperature variation have been documented – counter-gradient (or co-gradient) variation, and local adaptation. To determine how natural selection has shaped life history variation in a burying beetle, Nicrophorus orbicollis, we quantified lifetime patterns of reproduction in two populations that represent the geographic and temperature extremes occupied by the species. Lifetime reproduction was quantified at two temperatures that represented conditions typical for each population. Burying beetles from different extremes of their geographic range show considerable variation …

Map Kinase Signaling In Plant Responses To Biotic Stress, Carlton James Bequette

Theses and Dissertations

Plants must be able to perceive and properly respond to a multitude of environmental conditions and produce appropriate cellular responses for optimal growth and reproduction. Mitogen-activated protein kinase (MAPK) phosphorylation cascades are critical components of signal transduction networks that mediate cellular responses to a wide range of both biotic and abiotic extracellular stimuli. This thesis presents an investigation of three novel aspects of MAPK signaling, the role of MAPKs in the regulation of cell death, the organization of MAPKs in a multi-protein complex, and the negative regulation of MAPKs by MAPK phosphatases. In tomato, three MAPKs play an essential role …

The Effects Of Curcumin On The Expression Of P53 And Bcl-2 Oncoproteins On The Human Breast Carcinoma Cell Line Mda-Mb 468, Angelin S. Shajan

Theses and Dissertations

We studied the effects of curcumin on the proliferation and viability of MDA-MB-468 breast cancer cells and its effects on the expression ofBcl-2 and p53 proteins in these cells. Based on previous studies, we predicted a dose-dependent increase in p53 (tumor suppressor) expression, and a decrease in Bcl-2 (anti-apoptotic oncoprotein) expression. Briefly, MDA-MB468 cells were seeded into 12-well plates at 2.0 * 104 cells/well and allowed to grow for 72 hrs. Cells were treated with curcumin at 0, 25, 50 and 100 pM in triplicate at time zero and cultured for another 24 hours. All data were obtained using a …

Effects Of Tgf-Β1 And Il-33 On Mast Cell Function, Victor S. Ndaw

Theses and Dissertations

TGFβ is involved in many pathological conditions, including autoimmune disorders, cancer, and cardiovascular and allergic diseases. We have previously found that TGFβ can suppress IgE-mediated mast cell activation in human and mouse mast cells in vitro. IL-33 is a recently discovered member of the IL-1 family capable of inducing mast cell responses and enhancing IgE-mediated activation. In this study, we investigated the effects of TGFβ on IL-33-mediated mast cell activation. Bone marrow-derived mast cells cultured in TGFβ -1, -2, or -3 showed reduced IL-33-mediated production of TNF, IL-6, IL-13 and MCP-1, in a concentration-dependent manner. Furthermore, TGFβ also reduced …

Tipping The Balance Of Double-Strand Break Repair In Cells Modeling Hutchinson-Gilford Progeria Syndrome, Andrew Robert Patrick

Theses and Dissertations

Hutchinson-Gilford Progeria Syndrome is disease of highly accelerated aging. In addition to appearing physically old mere months after birth, patients suffer from maladies typical of the elderly, including heart attack and stroke, two factors which contribute to an average life expectancy of 14 years. The source of progeria has been identified as progerin, a defective variant of nuclear lamina protein lamin A. Progerin has also been found natively in healthy cells (concentration increasing with age), and is known to adversely affect nuclear morphology and chromosomal integrity. This thesis sought to investigate the effect of progerin upon which pathways were favored …

Species Responses To Climate Change And Environmental Heterogeneity: A Multi-Focal Approach, Megan Riley

Theses and Dissertations

Changes in global climate trends have the potential to influence diverse ecosystems at multiple levels of organization, from the species to the community. Changes in other environmental variables, such as those resulting from pollution and habitat modification, also have the potential to impact species fitness and alter species interactions. This dissertation employs a multi-focal approach to investigate species responses to two main topics: climate change and environmental heterogeneity. To investigate the first topic, this work focuses on the climate change-induced range expansion of the mangrove tree crab Aratus pisonii into novel salt marsh habitats. It investigates latitudinal patterns of life …

Tp53 And Hras Influence On Hpv16 E7 Expression In Hpv16-Transformed Human Keratinocytes, Nella Christie Delva

Theses and Dissertations

Head and Neck Squamous Carcinoma (HNSCC) is one of the most common cancers worldwide. HNSCC affects regions of the upper aerodigestive tract such as the lip, tongue, nasopharynx, oropharynx, larynx, and hypopharynx. About 25% of all HNSCC cases and up to 65% of Oropharyngeal Carcinoma (OPC) cases are positive for HPV DNA. African American patients, especially males, present primarily with HPV-negative HNSCC. HNSCC’s that are HPV-positive tend to be HPV-active at initial presentation: these cancers contain HPV DNA and express HPV RNA. However, recurring HPV-positive cancers of the head and neck are more often inactive: these tumors contain HPV DNA, …

The Evolutionary Biology Of Vision In Daphnia, Christopher S. Brandon

Theses and Dissertations

Eyes have attracted the attention of evolutionary biologist since the field’s infancy. In On the Origin of Species, in fact, Darwin famously remarked on the proposition that natural selection could engineer the eye, saying “[it is] absurd in the highest possible degree.” Though, he goes on to explain, beautifully and simply, how his theory of evolution by natural selection could produce such an organ. Indeed, eyes are remarkable examples of complex information acquisition systems that have evolved from simple beginnings. Eyes allow animals to extract environmental information from light, which informs physiological and behavioral responses to resources, predation, and mates. …

Potential Range Expansion Of The Invasive Lionfish In The Western Atlantic Ocean, Brian Grieve

Theses and Dissertations

Lionfish (Pterois volitans) are an invasive, predatory fish native to the reefs of the Indo-Pacific. In the mid-1980s, lionfish were introduced off the coast of Miami, FL and have since transformed many of the reef ecosystems throughout the Western Atlantic Ocean. Although lionfish are found year-round as far north as Cape Hatteras, NC, they are confined to the warm Gulf Stream during winter months. Seasonal inshore expansion is possible in the summer, and further poleward expansion is limited by cold bottom-water temperatures in winter. Here, I use an ensemble of 17 different climate models to project lionfish habitat by the …

Patterns Of Selection Amongst Dengue Virus Serotypes And Efficacy Of Computational Epitope Prediction Applications, April Christina Hall South

Theses and Dissertations

Dengue virus (DENV) is a mosquito-borne virus of global concern that leads to infections with symptoms ranging from high fevers and headaches to death. Current estimates place almost half the world’s population living in areas that are at-risk for infection by dengue and that area continues to expand over time. There are four distinct serotypes of dengue (DENV1, DENV2, DENV3, and DENV4). Disease severity from dengue infection is significantly worse if there is a secondary infection by a heterotypic serotype. The problems of increased severity with secondary infection as well as host immune response evasion by the virus itself have …

Speed And Resolution In The Age Of Technological Reproducibility, Shawn Taylor

Theses and Dissertations

The rate of acceleration of the biologic and synthetic world has for a while now, been in the process of exponentially speeding up, maxing out servers and landfills, merging with each other, destroying each other. The last prehistoric relics on Earth are absorbing the same oxygen, carbon dioxide and electronic waves in our biosphere as us. A degraded .jpeg enlarged to full screen on a Samsung 4K UHD HU8550 Series Smart TV - 85” Class (84.5” diag.). Within this composite ecology, the ancient limestone of the grand canyon competes with the iMax movie of itself, the production of Mac pros, …

Mysteries Of The Trypanosomatid Maxicircles: Characterization Of The Maxicircle Genomes And The Evolution Of Rna Editing In The Order Kinetoplastida, Preethi Ranganathan Iyengar

Theses and Dissertations

The trypanosomatid protists belonging to Order Kinetoplastida are some of the most successful parasites ever known to mankind. Their extreme physiological diversity and adaptability to different environmental conditions and host systems make them some of the most widespread parasites, causing deadly diseases in humans and other vertebrates.

This project focuses on their unique mitochondrion, called the kinetoplast, and more specifically involves the characterization of a part of their mitochondrial DNA (also called kinetoplast DNA or kDNA), the maxicircles, which are functional homologs of eukaryotic mitochondrial DNA in the kinetoplastid protists. We have sequenced and characterized the maxicircle genomes of 20 …

The Genetic Architecture Of Water-Use Efficiency Within And Between Two Natural Populations Of Foxtail Pine, Douglas E. Harwood

Theses and Dissertations

The goal of this project was to determine the genetic architecture of water-use efficiency (WUE) for foxtail pine, which included genomic loci, and effect sizes of this trait. Foxtail pine is a subalpine endemic conifer that inhabits two distinct regional populations separated by 500 km in the mountains of California. In order to achieve this goal, a robust linkage map containing thousands of genetic markers was created using four megagametophyte arrays ranging in size from approximately 70 to 95 megagametophytes. Quantitative trait loci (QTL) discovered for WUE were mapped along the linkage map using linear mixed models and five half-sibling …

Proof-Of-Concept Of Environmental Dna Tools For Atlantic Sturgeon Management, Jameson Hinkle

Theses and Dissertations

Abstract

The Atlantic Sturgeon (Acipenser oxyrinchus oxyrinchus, Mitchell) is an anadromous species that spawns in tidal freshwater rivers from Canada to Florida. Overfishing, river sedimentation and alteration of the river bottom have decreased Atlantic Sturgeon populations, and NOAA lists the species as endangered. Ecologists sometimes find it difficult to locate individuals of a species that is rare, endangered or invasive. The need for methods less invasive that can create more resolution of cryptic species presence is necessary. Environmental DNA (eDNA) is a non-invasive means of detecting rare, endangered, or invasive species by isolating nuclear or mitochondrial DNA (mtDNA) from the …

Consequences Of Vine Infestation: Linking Abiotic Influences And Biotic Interactions To Successional And Structural Changes In Coastal Communities, Spencer N. Bissett

Theses and Dissertations

Located at the interfaces of terrestrial and marine environments, coastal habitats are inherently vulnerable to the effects of global change. Barrier island systems in particular serve not only as protective buffers against storm events, but also as sentinel ecosystems for observation of the impacts of sea level rise, and of increasing storm frequency and intensity. In the mid-Atlantic region, shrub thickets of Morella species compose the dominant forest community. The often monospecific nature of these plant community assemblages is advantageous to ecological studies and cross-scale applications; the relatively low diversity facilitates transitions between scales. My objective was to investigate the …

Multi-Platform Arabinoxylan Scaffolds As Potential Wound Dressing Materials, Donald C. Aduba Jr

Theses and Dissertations

Biopolymers are becoming more attractive as advanced wound dressings because of their naturally derived origin, abundance, low cost and high compatibility with the wound environment. Arabinoxylan (AX) is a class of polysaccharide polymers derived from cereal grains that are primarily used in food products and cosmetic additives. Its application as a wound dressing material has yet to be realized. In this two-pronged project, arabinoxylan ferulate (AXF) was fabricated into electrospun fibers and gel foams to be evaluated as platforms for wound dressing materials. In the first study, AXF was electrospun with varying amounts of gelatin. In the second study, AXF …

Prothonotary Warbler Nestling Diet And Growth In Response To Variation In Aquatic And Terrestrial Food Availability, Jenna C. Dodson

Theses and Dissertations

Food supply has been suggested as the main determinant of reproductive success in birds. Riparian species can take advantage of seasonal pulses of both terrestrial and aquatic prey, though aquatic resources are often overlooked in studies of diet and reproductive ecology. This study investigates the flux of both aquatic (mayfly) and terrestrial (caterpillar) prey resources and nestling diet of the Prothonotary Warbler throughout the breeding season in two eastern Virginia sites. One site had significantly higher aquatic prey (mayfly) availability. Nestling diet was generally reflective of prey availability, and nestlings grew faster at the site with high aquatic prey availability. …

Effects Of The Algal Toxin Microcystin On Fishes In The James River, Virginia, Maxwell D. Haase

Theses and Dissertations

With the global rise in frequency of harmful algal blooms in estuarine environments comes an increase in prevalence of toxic metabolites, such as microcystin (MC), that some of the cyanobacteria involved will produce. At high concentrations, MC may accumulate in consumer tissues and have deleterious effects on organisms; however impacts of the toxin on aquatic living resources at ecologically relevant concentrations have not been widely documented. We analyzed the effects of MC on juveniles of five fish species from the James River, Virginia to determine if MC has the potential to impede growth. Using three separate experimental approaches, it was …

Marine Population Connectivity: Range Boundaries And Climate Change, Rhiannon Leigh Rognstad

Theses and Dissertations

Population connectivity, particularly in open systems, is an important metric for understanding population-level processes on both ecological and evolutionary timescales. In coastal marine systems, adults are typically sedentary and dispersal occurs primarily during a larval stage when individuals are transported in ocean currents. Because coastal marine populations exist as networks of interconnected subpopulations, variation in the magnitude and extent of population connectivity can have profound effects on population dynamics and species distribution limits. Connectivity is a complex process, affected by a multitude of factors, including adult inputs and physical dispersal, which operate at multiple scales and may interact. This dissertation …

Global Climate Change And The Southern Ocean: How Antarctic Fishes Physiologically Respond To A Changing Environment From The Cellular To The Organismal Level, Laura A. Enzor

Theses and Dissertations

Studies have projected that future changes in sea surface temperature and pCO2 levels will impact higher latitudes to a greater extent than in temperate regions. For notothenioid fishes of the Southern Ocean, evolution in extremely stable, cold waters has resulted in several adaptations which have left these fishes poorly prepared for global climate change. I have analyzed the metabolic and cellular response of Trematomus bernacchii, Pagothenia borchgrevinki and Trematomus newnesi to a long-term, multi-stressor scenario relevant to the predicted changes in the Southern Ocean. By combining whole animal respirometry with cellular level analysis of energy allocation, osmoregulatory mechanisms and cellular …