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Articles 1 - 30 of 40
Full-Text Articles in Life Sciences
Analysis Of Cellular Factors Involved In Adeno-Associated Virus Type 2 Entry, Cameron Dale Bess
Analysis Of Cellular Factors Involved In Adeno-Associated Virus Type 2 Entry, Cameron Dale Bess
Student Theses and Dissertations
The study of virus-host interactions has not only produced insights relevant to both preventative drug design and the emerging field of gene therapy, but it has also served as a valuable tool to the field of cell biology. The biological roles of many pathogen recognized cell-surface receptors have yet to be determined, yet are being exploited by pathogens to facilitate their entry and infection. Specifically a small family of sugar modified membrane protein known as heparan sulfate proteoglycans, have been shown to be a critical determinant in the efficiency of infection of many important pathogens. Adeno-associated virus type 2 (AAV) …
Synaptic Protein Profiling In The Mammalian Brain, Elizabeth Heller
Synaptic Protein Profiling In The Mammalian Brain, Elizabeth Heller
Student Theses and Dissertations
The mammalian central nervous system (CNS) contains billions of neurons each receiving thousands of synaptic inputs. Synapses are specified in part through the precise localization of synaptic proteins, yet it has not previously been possible to analyze the protein content of an individual class of synapses. In order to achieve this, we have used the BAC (bacterial artificial chromosome) transgenic approach to target particular neurons for expression of a given neurotransmitter receptor fused to an affinity tag. Immunohistochemistry of fixed brain tissue confirmed the correct localization of each synaptic fusion protein to the appropriate cell type and morphological structure. In …
Specification And Function Of Early Hair Follicle Stem Cells, Jonathan Nowak
Specification And Function Of Early Hair Follicle Stem Cells, Jonathan Nowak
Student Theses and Dissertations
In adult skin, multipotent epithelial stem cells (SCs) reside in a quiescent niche associated with each hair follicle termed the “bulge†and are essential for cyclic bouts of hair growth. Bulge stem cells can also contribute to sebaceous glands and the intefollicular epidermis when it is injured. While hair follicles begin to develop during embryogenesis, niche architecture becomes pronounced postnatally at the start of the first hair cycle. Whether SCs exist or function earlier is unknown. To determine if a stem cell population exists during follicle development, I conducted embryonic pulse-chase experiments to identify putative stem cells based on slow-cycling …
Biophysical Characterization Of Structure And Dynamics Of Nuclear Pore Complex Components, Martin Kampmann
Biophysical Characterization Of Structure And Dynamics Of Nuclear Pore Complex Components, Martin Kampmann
Student Theses and Dissertations
The Nuclear Pore Complex (NPC) mediates nucleo-cytoplasmic transport in all eukaryotes and is among the largest cellular assemblies of proteins, called nucleoporins (nups). The details of NPC architecture, dynamics, and mechanism are still unknown. NPCs can be dissected biochemically into distinct subcomplexes. One of the best-characterized subcomplexes, the Nup84 complex, consists of seven nups and was proposed to form a membrane-coating module of the NPC. I optimized the isolation of the heptameric complex from budding yeast and analyzed its structure by negative-stain electron microscopy (EM). My data confirm the previously reported flexible Y-shape. I solved the three-dimensional structures of two …
Characterization Of A Novel 53bp1-Dependent Mechanism That Promotes Non-Homologous End Joining Of Deprotected Telomeres By Increasing Chromatin Mobility, Nadya Dimitrova
Characterization Of A Novel 53bp1-Dependent Mechanism That Promotes Non-Homologous End Joining Of Deprotected Telomeres By Increasing Chromatin Mobility, Nadya Dimitrova
Student Theses and Dissertations
When a double-stranded break (DSB) occurs in mammalian genomes, the local chromatin is altered through the modification of histones (notably the phosphorylation of H2AX) and the binding of DNA damage response factors (e.g. MDC1, 53BP1). Although several lines of evidence have pointed to a role for some of these factors in DSB repair through non-homologous end-joining (NHEJ), the mechanism of their contribution has not been established. To study the regulation of NHEJ, we have used as a model system dysfunctional telomeres, which are uncapped by the removal of the shelterin component, TRF2. As a consequence of TRF2 loss, deprotected chromosome …
Architecture Of A Coat For The Nuclear Pore Membrane, Kuo-Chiang Hsia
Architecture Of A Coat For The Nuclear Pore Membrane, Kuo-Chiang Hsia
Student Theses and Dissertations
Nuclear pore complexes (NPCs) reside in the nuclear membrane and mediate macromolecules exchange between the nucleus and cytoplasm. Although the protein components of NPCs, termed collectively nucleoporin, have been identified, how nucleoporins arrange in NPC, however, is still an enigma. NPC is a highly symmetric protein complex, which contains an eight-fold rotational symmetry across the center of the pore and a two-fold symmetry in the plane of the nuclear envelope. In addition, according to electron microscopic reconstruction model, NPC can also be considered schematically as a series of concentric cylinders. A peripheral cylinder coating the nuclear pore membrane contains a …
Studies Of G-Protein Coupled Receptors Incorporated Into A Novel, Nanoscale, Membrane-Mimetic System, Sourabh Banerjee
Studies Of G-Protein Coupled Receptors Incorporated Into A Novel, Nanoscale, Membrane-Mimetic System, Sourabh Banerjee
Student Theses and Dissertations
From first principles of phospholipid – apolipoprotein A-I (apo A-I) interactions, we hypothesized that the amino acid sequence of apo A-I derived from a different species may exhibit improved properties compared to human apo A-I for the purpose of incorporation of G protein-coupled receptors (GPCRs) into homogeneous discoidal lipoprotein particles. We generated apolipoprotein A-I DNA derived from zebrafish (Danio rerio) using molecular cloning techniques and optimized a heterologous bacterial expression system, and protein purification and labeling scheme for obtaining high-yields of pure zebrafish apo A-I. We demonstrated that zebrafish apo A-I forms stable, homogeneous discoidal lipoprotein particles, which we termed …
The Role Of Adult Stem Cells And Tumor Necrosis Factor In Peripheral Neuropathy, Prabhjot Singh Dhadialla
The Role Of Adult Stem Cells And Tumor Necrosis Factor In Peripheral Neuropathy, Prabhjot Singh Dhadialla
Student Theses and Dissertations
Peripheral neuropathies are a significant cause of morbidity and mortality, with a population prevalence of 2,400 per 100,000 (2.4%) that increases in the elderly to 8,000 per 100,000 (8%)(C. N. Martyn and R. A. Hughes, 1997). The variations in symptom distribution and etiologic attribution have resulted in the classification of over 100 types of peripheral neuropathy with specific patterns of development and prognoses. In the first study, we use a mouse model of hereditary peripheral neuropathy that results in hind-limb paralysis to investigate the therapeutic efficacy of adult, adipose derived stem cells (ADSC). The paralyzed mice that received ADSC transplantation …
Transcriptional Regulation Of Adipocyte Function, Kivanc Birsoy
Transcriptional Regulation Of Adipocyte Function, Kivanc Birsoy
Student Theses and Dissertations
The increased white adipose tissue mass associated with obesity is the result of both hyperplasia and hypertrophy of adipocytes. While adipocyte development and transcriptional processes are well studied in vitro, regulation of in vivo genes (such as leptin), the identity of the adipocyte progenitor cells and the development of the adipose organ have not been defined invivo. In this thesis, firstly KLF4 was discovered to be an essential early regulator of adipogenesis. KLF4 together with Krox20 cooperatively transactivates C/EBPβ, suggesting that KLF4 and Krox20 are part of an immediate early transcriptional network. This network is upregulated in a lipodystrophic animal …
Regulated Histone H3 Proteolysis During Mouse Embryonic Stem Cell Differentiation, Elizabeth M. Duncan
Regulated Histone H3 Proteolysis During Mouse Embryonic Stem Cell Differentiation, Elizabeth M. Duncan
Student Theses and Dissertations
The association of genomic DNA with histone proteins in the three-dimensional structure known as chromatin is the central framework for “epigenetics,†which is defined as inherited phenotypes governed by differences that cannot be explained by changes in DNA sequence. In recent years, studies have shown that regulated changes in the chemical and physical properties of chromatin often lead to dynamic changes in many cellular processes, including development and differentiation, by affecting the accessibility of the genomic information stored in the DNA. The cell uses many different mechanisms to regulate chromatin in order to establish, maintain, and propagate patterns of gene …
Mechanism Of Signal Transduction By The Staphylococcus Aureus Quorum Sensing Receptor Agrc, Elizabeth A. George Cisar
Mechanism Of Signal Transduction By The Staphylococcus Aureus Quorum Sensing Receptor Agrc, Elizabeth A. George Cisar
Student Theses and Dissertations
Bacteria use receptor histidine kinases to sense extracellular cues and convert them into intracellular signaling events that allow them to respond to their environment. In Staphylococcus aureus, each individual cell must sense the size of its overall population in order to synchronize virulence factor expression with the entire population. This task is carried out by the accessory gene regulator (agr) quorum sensing system. The agr autoinducing peptide (AIP) pheromone activates the AgrC receptor histidine kinase, resulting in downstream modulation of virulence factor expression. As S. aureus is a dangerous pathogen, understanding virulence regulation is of great interest, and the agr …
Mechanistic And Physiological Studies Of The Insulin-Dependent Regulation Of Foxa2, Jessica Jean Howell
Mechanistic And Physiological Studies Of The Insulin-Dependent Regulation Of Foxa2, Jessica Jean Howell
Student Theses and Dissertations
The Forkhead box A2 transcription factor (Foxa2/HNF-3β) has been shown to be a key regulator of genes involved in the maintenance of glucose and lipid homeostasis in the liver, and is constitutively inactivated in several hyperinsulinemic/obese mouse models, thereby enhancing their metabolic phenotypes. Foxa2 is activated under fasting conditions, but is inhibited by insulin signaling via PI3K/Akt in a phosphorylation-dependent manner, which results in its nuclear exclusion. However, the mechanism and relative importance of nuclear export have not yet been elucidated. In addition, the existence and potential role of insulin-dependent regulation of Foxa2 have not been studied in other tissues …
Perceptual Learning Of Object Shape, Doruk Golcu
Perceptual Learning Of Object Shape, Doruk Golcu
Student Theses and Dissertations
Recognition of objects is accomplished through the use of cues that depend on internal representations of familiar shapes. We used a paradigm of perceptual learning during visual search to explore what features human observers use to identify objects. Human subjects were trained to search for a target object embedded in an array of distractors, until their performance improved from chance levels to over 80% of trials in an object specific manner. We determined the role of specific object components in the recognition of the object as a whole by measuring the transfer of learning from the trained object to other …
The Manipulation Of Apical Dendritic Plasticity And The Consequences For The Effects Of Chronic Stress, Trudy Mccall
The Manipulation Of Apical Dendritic Plasticity And The Consequences For The Effects Of Chronic Stress, Trudy Mccall
Student Theses and Dissertations
Pyramidal cell apical dendrites in region CA3 of the hippocampus of male rats collapse in size and complexity following chronic stress. These dendrites return to control sizes with a recovery period. This suggests that dendritic remodeling can function as a protective response mechanism, protecting the region from exposure to the increased amounts of excitatory amino acid released in stress. If this is the case, then a situation in which remodeling is prevented during stress should be more damaging to the long-term survival of the organism. To examine this, animals were treated with endo N, an enzyme that cleaves PSA from …
Transfer Properties Of The Hair Cell-Afferent Fiber Synapse, Erica C. Keen
Transfer Properties Of The Hair Cell-Afferent Fiber Synapse, Erica C. Keen
Student Theses and Dissertations
The perception of sound is initiated in the inner ear by the conversion of vibrational energy into a neural code, a transduction process achieved by the chemical synapses of hair cells in the auditory periphery. Thus, the operation of the hair cell’s presynaptic active zone is key to understanding auditory transduction. However, the lack of suitable experimental systems in which to investigate both the presynaptic and postsynaptic aspects of this synapse with high resolution has limited our understanding of its functional characteristics. This work describes the development of a novel in vitro preparation of the amphibian papilla from Rana catesbeiana …
Novel Interactions Of The Hormone Leptin Revealed By Pet Imaging In Rodents And Rhesus Macaques, Robert Richard Flavell
Novel Interactions Of The Hormone Leptin Revealed By Pet Imaging In Rodents And Rhesus Macaques, Robert Richard Flavell
Student Theses and Dissertations
Leptin is a polypeptide hormone, secreted principally by adipose tissue, which functions as an afferent signal in a feedback loop to maintain body weight and energy homeostasis. In addition to its well documented effects on food intake and energy expenditure, leptin modulates the function of many other physiological systems in mammals, through actions in the central nervous system and periphery. Remarkably, despite extensive studies on leptin receptor expression, the physiological biodistribution of the hormone remains essentially unknown. In order to characterize the distribution leptin in mammals, we have developed methodologies to radiolabel the hormone and visualize its biodistribution using positron …
Novel Roles For The Tissue Plasminogen Activator System In The Development Of Fetal Alcohol Syndrome And The Regulation Of Contextual Learning After Stress, Melissa Noel-Castro
Novel Roles For The Tissue Plasminogen Activator System In The Development Of Fetal Alcohol Syndrome And The Regulation Of Contextual Learning After Stress, Melissa Noel-Castro
Student Theses and Dissertations
Ethanol exposure during synaptogenesis can result in brain and behavior neurotoxic defects referred to as fetal alcohol syndrome (FAS). Since tissue plasminogen activator (tPA) has been implicated in mediating excitotoxic neurodegeneration we subjected neonatal WT and tPA-/- to an acute ethanol paradigm that serves as a model of FAS. We observed persistent upregulation of tPA and extensive neurodegeneration after ethanol in the forebrain of WT. However, tPA-/- mice were protected from neuronal death, suggesting tPA mediates ethanol-induced neurodegeneration and FAS in mice. Commensurate with neuronal death, we observed ethanol-induced cognitive impairments in adult WT, but not tPA-/- mice. To understand …
Fibrin Formation And Dissolution In The Progression Of Amyloid-Beta Pathology In Alzheimer's Disease, Justin Paul
Fibrin Formation And Dissolution In The Progression Of Amyloid-Beta Pathology In Alzheimer's Disease, Justin Paul
Student Theses and Dissertations
Alzheimer’s disease (AD) is a neurodegenerative disorder that leads to profound cognitive decline and eventually death. There are no effective long-term treatments or preventative measures available, and as the incidence and prevalence of the disease are increasing, new insights and tractable therapeutic targets are sorely needed. Genetic evidence indicates that a major cause of AD is the production of the amyloid-β (Aβ) peptide, which is proteolytically derived from the amyloid-β precursor protein. The Aβ peptide can oligomerize and be deposited as extracellular plaques in the brain and blood vessels, but the mechanism of how it leads to neuronal death is …
The Neural Circuitry Of Social Behavior In C. Elegans, Evan Z. Macosko
The Neural Circuitry Of Social Behavior In C. Elegans, Evan Z. Macosko
Student Theses and Dissertations
Most animal species, from simple invertebrates to complex mammals, require behavioral mechanisms to communicate with and respond to conspecifics, whether to mate, to assess predatory danger, or evaluate the nutritional quality of the surrounding environment. Understanding the molecular and cellular underpinnings of these social behaviors remains a central challenge in neurobiology. I used the nematode C. elegans as a model system to study the genetics and neural circuitry that underlie social behavior. First, I evaluated the behavioral responses of C. elegans to a nematode extract (deathmone), which served as a model for alarm pheromones in other animal species (chapter 2). …
Perceptual Learning, Long-Range Horizontal Connections And Top-Down Influences In Primary Visual Cortex, Valentin Piëch
Perceptual Learning, Long-Range Horizontal Connections And Top-Down Influences In Primary Visual Cortex, Valentin Piëch
Student Theses and Dissertations
The earliest cortical stage of visual processing, the primary visual cortex, has long been seen as a static preprocessor that finds local edges and their orientation like a linear filter bank, and passes this information on to downstream visual areas. This view has been challenged in recent years since the discovery of contextual influences, that is, interactions between the responses of neurons that encode for non-overlapping adjacent areas of visual space, and their anatomical substrate, long-range horizontal connections. These contextual interactions have been shown in awake behaving primates to be modulated depending on the task the animals are performing. A …
The Role And Fate Of Branch Site-U2 Snrna Interaction During Pre-Mrna Splicing, Duncan Smith
The Role And Fate Of Branch Site-U2 Snrna Interaction During Pre-Mrna Splicing, Duncan Smith
Student Theses and Dissertations
Many details of the conformational dynamics underlying transitions during premRNA splicing, particularly during the catalytic phase, remain unclear despite our deep knowledge of spliceosome composition. The complex assembly phase that precedes catalysis, and the involvement of several motifs in multiple interactions along the splicing pathway, exacerbate the difficulty of accessing splicing catalysis experimentally. snRNAs likely form some or all of the spliceosomal active site. We attempted to establish an snRNA-only splicing system as a means to bypass assembly and recapitulate splicing catalysis. Our approach, however, yielded a 2’-3’ bondforming ribozyme activity in a linker region in our fused snRNA construct; …
Regulation Of Apoptosis By Xiap Ubiquitin- Ligase Activity, Andrew James Schile
Regulation Of Apoptosis By Xiap Ubiquitin- Ligase Activity, Andrew James Schile
Student Theses and Dissertations
Virtually all animal cells have the known ability to self-destruct by undergoing apoptosis, a morphologically distinct form of programmed cell death. The proper regulation of apoptosis is critical for both development and tissue homeostasis, and inhibition of apoptosis contributes to the development and progression of cancer. Inhibitor of Apoptosis Proteins (IAPs) can bind to and inhibit caspases, the key executioners of apoptosis. Because IAPs are frequently over-expressed in human tumors, they have become major pharmacological targets for developing new cancer therapeutics. Many IAPs contain RING domains that function as E3 ubiquitin-ligases to regulate the abundance of IAPs themselves and their …
Population Dynamics In A Model Closed Ecosystem, Doeke Romke Hekstra
Population Dynamics In A Model Closed Ecosystem, Doeke Romke Hekstra
Student Theses and Dissertations
For almost any species in any environment, it is nearly impossible to predict its fitness from molecular knowledge. If fitness is not to be a mere tautology, reproducible measurements of the survival and reproduction of populations are needed over many generations. Laboratory microbial ecosystems afford the short time and length scales required for such measurements. Their conventional implementations, batch cultures with period refreshment of growth medium or chemostats with continuous refreshment, have a number of disadvantages, such as the introduction of additional frequencies, selection for surface growth and the distortion of chemical interactions. In closed ecosystems free energy is instead …
Hierarchy And Cis-Regulation In Drosophila Segmentation: Rules For Pattern Formation And Clues To Evolution, Mark David Schroeder
Hierarchy And Cis-Regulation In Drosophila Segmentation: Rules For Pattern Formation And Clues To Evolution, Mark David Schroeder
Student Theses and Dissertations
In few systems is it possible to analyze the global cis-regulatory structure of developmental transcription networks. One system where this is in principle possible is segmentation in Drosophila melanogaster, although to date such an undertaking has not been attempted. Here using computational algorithms to analyze the transcriptional regulatory regions of genes of the gap and pair rule classes such an analysis is carried out. Computational analysis, transgenic reporter element assays, site directed mutagenesis, genetics, and time courses of in situ hybridizations of central genes in carefully staged embryos are combined to understand how the cis-elements function together to achieve patterning …
Cell Size Control And Asymmetric Cell Fates In Start Of The Saccharomyces Cerevisiae Cell Cycle, Talia, Stefano Di
Cell Size Control And Asymmetric Cell Fates In Start Of The Saccharomyces Cerevisiae Cell Cycle, Talia, Stefano Di
Student Theses and Dissertations
Understanding the molecular and biophysical mechanisms that couple the process of cell growth to cell division is one of the major challenges of modern cell biology. Saccharomyces cerevisiae (budding yeast) has been an important model organism to study the coupling between cell growth and cell division. The insights obtained from studies of this unicellular organism have been pivotal for related studies in animal systems. The classical picture that emerged from studies in budding yeast was that cell cycle commitment in G1, at a point called Start, requires growth to a critical cell size. This deterministic model did not address how …
Peak Mitotic Cyclin Permits Mitotic Exit, Benjamin Drapkin
Peak Mitotic Cyclin Permits Mitotic Exit, Benjamin Drapkin
Student Theses and Dissertations
In eukaryotes, DNA replication, mitosis, and cytokinesis are all regulated by Cyclin-dependent kinase (Cdk). Cyclin/Cdk complexes promote replication origin firing and mitotic entry, and conversely, inhibit pre-replication origin loading and exit from mitosis. Cyclin synthesis and degradation, Cdk phosphorylation and Cdk inhibitors are controlled such that Cdk activity oscillates once per cell cycle. Little is known about the quantitative relationship between the level of Cdk activity and the occurrence, rate, and coordination of cell cycle events. We have addressed this question in Saccharomyces cerevisiae by introducing titrated levels of undegradable mitotic B-cyclin (Clb2kd) in cells prior to release of a …
Glia Are Required For Sensory Neuron Morphology And Function In Caenorhabditis Elegans, Taulant Bacaj
Glia Are Required For Sensory Neuron Morphology And Function In Caenorhabditis Elegans, Taulant Bacaj
Student Theses and Dissertations
The nervous system emerges from the coordinated development of neurons and glia. To better understand the processes that enable nervous system development and function we have studied the sensory organs of Caenorhabditis elegans because their anatomy and function are well-characterized. Specifically, we have focused on two aspects of sensory organs: how do glia interact with neurons to enable proper development and function and how are sensory cilia generated. To uncover any glial roles, we ablated the major glial cell of the amphid sensilla. Embryonic glial ablation did not affect neuronal survival and resulted in sensory neuron dendrites that were far …
Regulation Of Immunoglobulin Gene Diversification By Noncoding Rna's, Grace Teng
Regulation Of Immunoglobulin Gene Diversification By Noncoding Rna's, Grace Teng
Student Theses and Dissertations
Small regulatory RNAs supplement the canonical pathways of gene regulation through diverse mechanisms of transcriptional, post-transcriptional, and post-translational silencing. These mechanisms range from “classical†RNA interference (RNAi), to gene repression by microRNAs (miRNAs), to maintenance of genomic stability by repeatassociated small RNAs. Here, I describe the contribution of miRNA-mediated regulation to a specific case of gene expression that requires significant somatic alteration of the genetic code. B lymphocytes perform somatic hypermutation (SHM) and class switch recombination (CSR) of the immunoglobulin locus to generate an antibody repertoire diverse in both affinity and function. These somatic diversification processes are catalyzed by activation-induced …
Physiological Effects Of Estradiol In The Mouse Hippocampal Formation, Joanna L. Spencer
Physiological Effects Of Estradiol In The Mouse Hippocampal Formation, Joanna L. Spencer
Student Theses and Dissertations
At several points in a woman’s life, changes in circulating estradiol are associated with disturbances in mood and cognitive function. To determine the biological basis of these behavioral changes, researchers have concentrated on the hippocampal formation, a medial temporal lobe structure involved in the regulation of mood and cognition in humans. It is now clear that estradiol increases the substrates of hippocampal synaptic plasticity, including dendritic spine density, synapse density, and synaptic protein expression. In some cases, these changes are associated with alterations in mood and hippocampal-dependent learning and memory. The upstream mediators of these estradiol effects remain unknown, but …
Regulation Of The Heterochromatin Protein 1 By Phosphorylation Of Histone H3 And The Hp1 Hinge Domain, Holger Dormann
Regulation Of The Heterochromatin Protein 1 By Phosphorylation Of Histone H3 And The Hp1 Hinge Domain, Holger Dormann
Student Theses and Dissertations
Chromatin, a polymer formed from DNA, histones, and associated proteins, is the physiological form of genetic information in all eukaryotic cells. Posttranslational modification of histones, such as acetylation, methylation, and phosphorylation, regulates various DNA-dependent processes, ranging from transcription to replication, DNA repair, and apoptosis. A key mechanism by which histone modifications exert these effects is by recruitment of specific binding partners (effector proteins), that in turn direct downstream functions. Insight into the underlying mechanisms are of great importance for a full understanding of chromatin structure and function. One of these effector proteins, Heterochromatin Protein 1 (HP1), plays important roles in …