Browsing by Subject "Disease Modeling"
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Item Alzheimer's Fibroblasts are More Susceptible to Oxidative Stress(2001-05-01) Marshall, Pamela L.; Neeraj Agarwal; Robert GracyMarshall, Pamela L., Alzheimer’s Fibroblasts Are More Susceptible to Oxidative Stress. Master’s of Science (Biomedical Sciences). May 2001. Recent evidence indicates that oxidative stress contributes to neuronal death in Alzheimer’s disease (AD). In addition, it has been suggested that AD is a systemic illness in which the development of the disease is only visible in the brain. The aim of this research is to develop experimental procedures using a simple cell model, the fibroblast, to determine if proteins derived from AD skin fibroblasts are more sensitive to oxidation by reactive oxygen species than non-AD cells, and to assess the ability of antioxidants to prevent this oxidative damage in AD fibroblasts. Preliminary findings suggest that changes in sensitivity are already detectable in fibroblasts from AD patients, probably as a consequence of genetic component as well as other risk factors. Therefore, this biochemical marker might have the potential for identifying individuals at risk for AD.Item Differential Gene Expression Profiling in a Small Animal Model of Progressively Pacing-Induced Heart Failure(2006-06-01) Selby, Donald Evan; Stephen R. Grant; Patricia A. Gwirtz; Dan DimitrijevichDonald Evan Selby, Differential Gene Expression Profiling in a Small Animal Model of Progressively Pacing-Induced Heart Failure. Doctor of Philosophy (Biomedical Sciences), July 2006, 235 pp, 4 tables, 35 illustrations, references, 328 titles. Pacing induced tachycardia (PIT), in mammals, is known to cause a change from normal heart function to early left ventricular dysfunction. Progression to heart failure in experimental animals, such as dogs, pigs, and sheep, takes place in a relatively short period of time compared to the disease development observed in humans. Due to the cost and nature of using such animals, there is a need for a small animal model of PIT, which would delineate the etiology of the disease state by impairing the systolic function. The mode of action of overpacing inducement of cardiomyopathy, as the data suggests, may be through a sarcomere stretch sensor and its length-dependent signaling mechanism. In this study, an internal electrical-overpacing of an isogenic rabbit strain over a 52-day period was used to initiate a pathology consistent with human CHF. The data presented demonstrated that PIT causes alterations in the systolic ability of the heart, observed as reduced fractional shortening of the heart. This is seen in changes of the message pool population for proteins of the contractile architecture. Initially the heart is being paced rapidly and therefore there is insufficient time to get blood into the chamber. Thus, the data suggests that a mechanical stretch sensor is the process by which overpacing the heart leads to changes in gene expression which ultimately cause a compounding cellular condition which exists during heart failure. The data shows that there are gene isoform ratio changes that occur as the disease develops these include changes in differential expression of cardiac titin alternative splicing isoforms. The data suggests that there is also isoform switching occurring with alternative splicing of the gene encoding for SERCA2a, the probe 1587641_at shows a moderate decrease in expression and using BLAST for this probe this sequence is homologous to an alternative splicing variant of SERCA2a of the rabbit accession number J04703. The data shows that ferritin heavy chain also has an alternative splicing variant that are differentially regulated, this dysregulation of the isoform ratio may be linked to ADAMSTS1, a disintegrin and metalloproteinase isoform 1, which is seen to be downregulated in the data, these play a role in negative regulation of cellular proliferation. In addition to these detected isoform changes in the ratios of alternative splice variants changes are seen in genes linked to sarcomere integrity such as dystrophin probe 1582958_at is significantly increased in its expression, also integrin beta-1 probe 1584175)at shows a marginal increase in expression. The protease calpain probe 1604384)at, which uses a substrate the aforementioned integrin, dystrophin, and titin is also significantly upregulated in the data. Interestingly calpastatin, probe 1591603_at the inhibitor of calpain is marginally increased in its expression. Only recently has titin become to be appreciated as the protein that is responsible for the Frank Starling law as it undergoes an isoform ratio change as heart failure develops. These changes are initially caused by changes in ion concentration and stress upon the contractile proteins but as seen in the study, leads to altered gene expression. In this model, these gene alterations lead to diastolic dysfunction and the compounded problems constitute heart failure. This work shows that heart failure induced by over-pacing creates physical demands upon the framework of the heart and these physical stresses are transmitted through mechanical sensors leading to differential expression of the message pools for proteins involved in the way the heart contracts, and fills upon relaxation which ultimately ends in a heart that can do neither, thus leading to death.Item Extracellular PACE4 is increased following transient oxygen glucose deprivation in Optic Nerve Astrocytes(2008-05-01) Fuller, John Anthony; Wordinger, Robert J.; Clark, Abbot F.; Krishnamoorthy, Raghu R.Fuller, John Anthony Extracellular PACE4 is increased following transient oxygen glucose deprivation in Optic Nerve Astrocytes. Doctor of Philosophy (Biomedical Sciences), May, 2008, 140 pp., 2 tables, 25 illustrations, bibliography, 218 titles. Primary Open Angle Glaucoma (POAG) is a family of heterogeneous optic neuropathies characterized by progressive retinal ganglion cell (RGC) death that leads to peripheral vision loss and eventually blindness. Various risk factors are associated with glaucoma, however the molecular mechanisms leading to RGC cell death remain unknown. The optic nerve serves as the conduit for the transmission of retinal ganglion action potentials to the brain. The cells that compromise the optic nerve form a scaffold that forms a physical support for the RGC axons. One cell type found throughout the optic nerve and associated with the RGC axon is the optic nerve astrocyte (ONA). Astrocytes are a predominant cell throughout the CNS and are believed to play crucial roles in metabolic, growth factor, and structural support, and respond to protect neurons during injury. The neuronal-glial interface in the optic nerve is poorly understood and believed to plan an important role in POAG pathophysiology, as unmyelenated RGC axons have direct contact with astrocyte processes. IN this study, the subtilisin-like Proprotein Convertases, (SPC) a family of proteases responsible for cleaving a wide variety of protein substrates, were examined in the retina and optic nerve head. PACE4, an SPC found to be secreted and active in the extracellular matrix was found to be highly expressed in the optic nerve, and colocalized to Mϋller cells in the retina and astrocytes in the optic nerve. Exposure of primary optic nerve astrocytes to oxygen-glucose deprivation (OGD) induces an increase in PACE4 mRNA. Furthermore, protein levels of extracellular, processed PACE4 increase following transient ODG, whereas the pro form of the molecule is degraded, and is believed to be chaperoned by the cleaved cysteine rich domain, a product found at high levels in the optic nerve in situ and the ONA in vitro. Due to the extracellular activity of PACE4, we hypothesized that it may regulate the bioactivity of TGF-β2, a growth factor believed to be involved in glaucoma-associated ONH remodeling by inducing the production of extracellular matrix (ECM). When PACE4 is inhibited via siRNA-mediated knockdown, as well as extracellular inactivation, TGF-β2 levels decrease. In addition, fibronectin, a major component of the ECM, is decreased. Furthermore, there is an increase in latent TGF-β2 secreted from the cell. It is therefore possible that PACE4 plays an active role in extracellular growth factor maturation, and may be a central mediator for growth factor bioactivity in the glaucomatous ONA.Item Mechanisms of Photoreceptor Cell Apoptosis(2000-05-01) Crawford, Matthew John; Neeraj Agarwal; Victoria Rudick; Raghu KrishnamoorthyCrawford, Matthew John, Mechanisms of Photoreceptor Cell Apoptosis. Doctor of Philosophy (Biomedical Sciences), May 2000; 168 pp; 3 tables; 23 figures; bibliography, 282 titles. Photoreceptor cell death mediated by programmed cell death pathways is responsible for many disease states of the retina, which result in vision loss. Examples of this include retinal dystrophies and age-related macular degeneration. Correspondingly, the understanding of programmed cell death, or apoptosis, in these cells is important in the formulation of preventative and treatment options. The goals of this dissertation are to characterize a suitable in vitro photoreceptor cell model and explore the molecular mechanisms resulting in apoptotic cell death secondary to oxidative cell death paradigm. Means of interrupting the cell death process were also investigated. An immortalized clonal mouse retinal cell line was shown to express photoreceptor-specific genes and proteins by RT-PCR amplification, Western blot analysis, and immunocytochemical localization. Exposing these cultured cells to visible light resulted in oxidative stress, as exhibited by elevated malonyldialdehyde and reduced gluthathione levels, as well light exposure-dependent apoptosis was shown using multiple techniques which identified fragmentation of chromosomal DNA, a key finding in the apoptotic cell death process. Molecular regulators of apoptotic cell death, including bcl-2 family proto-oncogenes and the nuclear transcription factor NF-kB, were found to be important in oxidative stress-induced pathogenesis of 661 W photoreceptor cells. mRNA and protein levels of the anti-apoptotic proto-oncogene bcl-2 declined following oxidative stress disturbing the balance proto-oncogene regulators and initiating the apoptotic pathway. The nuclear transcription factor NF-kB was found to be constitutionally expressed in the photoreceptor cells with its down-regulation during apoptosis. Permanent transfection of the photoreceptor cells with bcl-2 gene imparted protection from apoptosis and sustained NF-kB levels. The results presented in this dissertation help define the molecular mechanisms which occur during apoptosis of photoreceptor cells. Photo-oxidative stress results in programmed cell death mediated through changes in NF-kB binding activity and bcl-2 family genes. The involvement of caspase-1 in the degradation of NF-kB and the execution of apoptosis is also demonstrated. Over-expression of the proto-oncogene bcl-2 interrupts the apoptotic events, protecting against down-modulation of NF-kb binding activity and cell death. Our proposed mechanism for apoptosis in photoreceptor cells provides several points at which targeted gene expression (bcl-2 or NF-kB), or pharmaceuticals (anti-oxidants, caspase inhibitors, or calcium channel blockers) may prevent apoptotic cell death.Item Molecular Regulation of Wound Contraction and Scar Formation Using a Three-Dimensional Connective Tissue Model(2002-12-01) Kern, Jami RaDel; Thomas Yorio; Robert W. Gracy; Peter B. RavenKern, Jami RaDel, Molecular Regulation of Wound Contraction and Scar Formation Using a Three-Dimensional Connective Tissue Model. Doctor of Philosophy (Biomedical Sciences, Biochemistry and Molecular Biology), December 2002, 156 pp., 1 table, 27 illustrations, references, 112 titles. The focus of these studies was to characterize a novel connective tissue model for use in experiments examining possible contraction initiators in the wound healing process, i.e. endothelin-1 (ET-1). Through these studies, it has been shown that use of a telomerized dermal fibroblast cell line addresses the concerns relating to variations due to heterogeneity of normal human cells cultured in vitro, without creating a cancerous cell line or interfering with normal phenotypic changes. In addition, the incorporation of telomerized cells into our TE, which does not spontaneously contract (US Patent #6471958), provides a unique model to study the contraction and scar formation process. Using the TE populated with hTERT fibroblasts, an innovative technique was developed to identify the initiation of tissue contraction using an optical fiber interferometry system. The process allows observation of contraction within five minutes of stimulus addition and also enables continuous data capture over a period of several hours. The greatest strength of this system is its sensitivity, since optic interferometer allows measurement of displacement (contraction) to the tens of nanometers. Along those lines, the current studies have identified ET-1 as a potential early initiator in wound healing and suggest a novel pathway through which it functions. This proposed mechanism includes both direct effects of ET-1 through the Rho-associated kinase pathway and indirect effects potentiated by TGF-β. Future studies addressing whether TGF-β converges on the Rho-associated kinase pathway or acts independently through other signaling mechanisms should be initiated. The discovery of early initiators of tissue contraction is essential in the identification of potential therapeutic targets in the quest to reduce prolonged and severe tissue contracture and scaring.Item Studies of Protein F1 (GAP-43) Expression and Function in Spinal Neuronal Cultures(1994-08-01) El-Badawy, Hassan M.E. Azzazy; Ming-Chi Wu; Guenter W. Gross; Scott NortonEl-Badawy, Hassan M. E. Azzazy, Studies of Protein F1 (GAP-43) Expression and Function in Spinal Neuronal Cultures. Doctor of Philosophy (Biochemistry and Molecular Biology), August 1994, 167 pp., 32 illustrations, References, 194 titles. Protein F1 (GAP-43, B-50, neuromodulin) is a membrane-bound phosphoprotein that has been studied mainly in neurons and is implicated in synaptic plasticity, axonal growth and regeneration, and neurotransmitter release. In this study, a 21 amino acid polypeptide that corresponds to the C-terminus sequence of protein F1 and contains a potential PKC phosphorylation sequence (SXR) was synthesized. The synthetic peptide was phosphorylated by rat PKC in a concentration-dependent manner suggesting that this site in the intact protein may be phosphorylated by PKC in vivo. Polyclonal antibodies against the peptide were produced in a rabbit and used to: (i) recognize native non-phosphorylated protein F1 purified from rat brain, (ii) immunoprecipitate phosphorylated protein F1, and (iii) stain the cell bodies and neuritis of cultured neurons. Electron microscopic studies revealed intracellular protein F1 immunoreactivity but no specific subcellular association of the gold label could be demonstrated. The antibodies were also used to compare protein F1 levels during the development of spinal neurons in culture and in vivo. The highest levels of protein F1 were detected by ELISA, at 2 days in culture. These results are in accordance with previous reports that correlate high expression of protein F1 to neurite outgrowth. In vivo, however, protein F1 reached maximal level at one day after parturition. Two approaches were utilized to investigate the potential physiological functions of protein F1 in spinal neurons networks. First, interaction of positively charged, rhodamine-labeled liposomes with spinal neurons was characterized by fluorescence microscopy and electrophysiological recording. Uniform, non-toxic, and preferential interaction of liposomes with spinal neurons over glia was established. These liposomes were used to deliver anti-protein F1 antibodies into spinal neurons but did not affect neurite formation by these cells. Second, antisense oligodeoxynucleotides internalized into spinal neurons in order to interfere with protein F1 expression had no effect on the development of these cells in culture. Data from this study suggest that Ser-210 at the C-terminus of protein F1 may be a substrate for PKC phosphorylation in vivo. Antibodies raised against F1 peptide revealed protein F1 immunoreactivity that outlined cell bodies and neuritis of cultured spinal neurons. Positively charged liposomes were characterized as a potential delivery system for macromolecules into spinal neurons. Protein F1 levels were shown to be developmentally regulated in mouse spinal neurons in culture and in vivo. Finally, the use of antisense oligodeoxynucleotides against protein F1 mRNA revealed that protein F1 may not be essential for neurite outgrowth of mouse spinal neurons in culture.Item The Effects of Short-Term Intermittent Hypoxic Apneas on Sympathetic Nerve Activity and the Chemoreflex Control of Sympathetic Nerve Activity in Humans(2004-05-01) Cutler, Michael J.; Smith, Michael L.; Raven, Peter B.; Downey, H. FredCutler, Michael J., The Effects of Short-Term Intermittent Hypoxic Apneas on Sympathetic Nerve Activity and the Chemorelex Control of Sympathetic Nerve Activity in Humans. Doctor of Philosophy (Integrative Physiology), May 2004. Obstructive sleep apnea is associated with sustained elevation of muscle sympathetic nerve activity (MSNA) and altered chemoreflex control of MSNA both of which likely play an important role in the development of hypertension in these patients. Hypoxia is postulated to be primary stimulus for elevated daytime MSNA and altered chemoreflex control of MSNA both of which likely play an important role in the development of hypertension in these patients. Hypoxia is postulated to be the primary stimulus for elevated daytime MSNA and altered chemoreflex control of MSNA in OSA patients. Recently, short-term exposure to hypoxia was shown to produce sustained elevation of MSNA. Therefore, we studied the effects of 20 min of intermittent voluntary hypoxic apneas (to mimic OSA) on MSNA and the chemoreflex control of MSNA during 180 min post exposure. Also, we compared MSNA and chemoreflex control of MSNA for 180 min following either 20 min of intermittent voluntary hypoxic apneas, hypercapnic hypoxia, or isocapnic hypoxia. Consistent with our hypotheses, both total MSNA and MSNA burst frequency were elevated following 20 min of intermittent hypoxic apnea compared to baseline (p [less than] 0.05). Both total MSNA and MSNA burst frequency remained elevated throughout the 180 min recovery period and were statistically different from time control subjects throughout this period (p [less than] 0.05). Additionally, a significant main effect for chemoreflex control of SNA was observed following 20 min of intermittent hypoxic apneas (p [less than] 0.001). Specifically, the MSNA response to a single hypoxic apnea was attenuated 1 min post exposure compared to baseline (p [less than] 0.001), became augmented within 30 min of recovery, and remained augmented through 165 min of recovery (p [less than] 0.05). Finally, comparison of treatment groups (hypoxic apnea, hypercapnic hypoxia, and isocapnic hypoxia) revealed no differences in resting MSNA (p=0.50) and the chemoreflex control of MSNA (p=0.69) during recovery. Therefore, these data support the hypothesis that short-term exposure to intermittent hypoxic apneas resulted in sustained elevation of MSNA and altered chemoreflex control of MSNA. Furthermore, these responses appear to be mediated by hypoxia.Item The Influence of Aging and Glycation on Protein-Thiol Mixed Disulfides in the Eye Lens(1994-06-01) Dickerson Jr., Jaime E.; McConathy, Walter J.; Yorio, Thomas; Lou, MarjorieJaime E. Dickerson, Jr., The Influence of Aging and Glycation on Protein-Thiol Mixed Disulfides in the Eye Lens. Doctor of Philosophy (Biomedical Sciences), June, 1994, 163 pp., 9 tables, 28 illustrations, bibliography, 116 titles. The human lens is continually growing. As new cells are formed they differentiate into fiber cells which have no organelles, no protein synthesis or turnover. Lens protein aging involves formation of very large aggregations and insoluble complexes. These are held together through disulfide linkages. Reduced gluthathione (GSH) is present in high concentrations. The oxidized form, (GSSG), (5% of the total) can form mixed disulfides with proteins. This can destabilize the protein conformation. Accumulation of mixed disulfides may increase the potential for further modification. The participation of a PSSG (protein/gluthathione mixed disulfide) in the formation of a protein-protein disulfide becomes increasingly likely. The purpose of this work is to document PSSG and protein-cysteine mixed disulfide (PSSC) accumulation in human lenses (through eight decades), and to identify a third mixed disulfide discovered in this research. The free thiol molecules GSH and cysteine were also quantitated for normal and cataractous lenses. Glycation may alter conformation similar to mixed disulfides and potentiate mixed or protein-protein disulfide formation. This model was evaluated two ways. First, purified alpha crystalline was incubated with ascorbate and conformational changes were evaluated with CD spectroscopy. Second, rat lenses were cultured under high sugar conditions to determine if the resulting glycation influenced the level of mixed disulfides. Conversely, the effect of prior mixed disulfide formation on the extent of glycation in another purified crystalline, gamma, was evaluated. The results indicate: GSH declines in the lens with age, cysteine exists in the lens albeit at relatively low levels, PSSG shows a triphasic pattern of accumulation, PSSC accumulated linearly with increasing age, the existence of a third mixed disulfide species, gamma glutamylcysteine mixed disulfide, detected in old or cataractous lenses, has been confirmed, glycation by ascorbic acid alters α- crystalline secondary structure, the influence of glycation is minimal on mixed disulfide formation, mixed disulfide formation affects glycation of gamma crystalline.