Browsing by Subject "Cell Anatomy"
Now showing 1 - 20 of 39
- Results Per Page
- Sort Options
Item A Novel sRNA Member of the Carbon Storage Regulatory System of Escherichia Coli(2002-12-01) Weilbacher, Thomas; Jerry SimeckaWeilbacher, Thomas S., A Novel sRNA Member of the Carbon Storage Regulatory System of Escherichi coli. Master of Science (Microbiology & Immunology), December, 2002, 57 pp., 2 tables, 12 illustrations, bibliography, 44 titles. Small untranslated RNAs (sRNAs) perform a variety of important functions in bacterial systems. The 245 nt sRNA of Escherichia coli K-12, CsrC, was uncovered using a genetic screen for genes that regulate glycogen biosynthesis. CsrC RNA binds multiple copies of CsrA, a protein that post-transcriptionally regulates central carbon flux, biofilm formation, and motility in E. coli. CsrC antagonizes the regulatory effects of CsrA, presumably by sequestering this protein. The discovery of CsrC is intriguing, in that a similar sRNA, CsrB, performs essentially the same function. Both of these sRNAs possess similar imperfect repeat sequences (18 in CsrB, 9 in CsrC), primarily localized in the loops of predicted hairpins, which may serve as CsrA binding elements. Transcription of csrC increases as the culture approaches the stationary phase of growth and is activated by CsrA and the response regulator UvrY. Complementation and in vitro transcription-translation experiments reveal that CsrA effects on csrC are mediated indirectly, through UvrY. Because CsrB and CsrC antagonize the activity of CsrA and are dependent on CsrA for their synthesis, a csrB null mutation causes a modest compensatory increase in CsrC levels and vice versa. An updated model for the signaling circuitry of the Csr system is discussed.Item Alterations in mRNA Levels of Selected Gene Products During Hypoglycemia, Hypoxia, and Ischemia Induced Apoptosis of Cultured Rat Retinal Ganglion Cells(2001-08-01) Vopat, Kelly S.; Agarwal, Neeraj; Wordinger, Robert J.; Pang, Iok-HouVopat, K., Alterations in mRNA Levels of Selected Gene Products during Hypoglycemia, Hypoxia, and Ischemia Induced Apoptosis of Cultured Rat Retinal Ganglion Cells. Master of Science (Biomedical Science), August 2001. 54 pp., 2 tables, 10 illustrations, bibliography, 105 titles. In order to explore the mechanisms involved in the signal transduction pathways of ischemia-induced apoptosis of RGCs in glaucoma, an in vitro ischmia model of transformed rat retinal ganglion cells (RGC-5) was utilized. RGC-5 cells were exposed to hypoglycemia, hypoxia, and ischemia for six hours. Hypoxia and ischemia resulted in apoptosis of RGC-5 cells as determined by TUNEL assay. The bax mRNA levels increased significantly in cells exposed to hypoxia. The mRNA levels of hemoxygenase, c-fos HSP 70, and BDNF showed a trend of increase in both the hypoxic and ischemic conditions. These results demonstrate that retinal ganglion cells undergo apoptosis in hypoxic conditions likely via an increase in bax/bcl-2. The up-regulation of BDNF and some stress proteins may be part of a cellular rescue effort trying to overcome the damage created by hypoxic and ischemic stresses.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 Anatomical and Biochemical Characterization of the Porcine Spinal Arachnoid(1994-06-01) Taylor, Martin T.; Turner, James; Yorio, Thomas; Wordinger, Robert J.Taylor, Martin T., Anatomical and Biochemical Characterization of the Porcine Spinal Arachnoid. Doctor of Philosophy (Biomedical Sciences), June, 1994. Mast cell products modulate many biologic barrier systems. In the central nervous system (CNS) two such barriers are the blood-brain barrier (B-B-B) and its analogous cerebrospinal fluid-blood barrier (CSF-B-B). Published research has demonstrated that mast cell products increase the permeability of the BBB, but no comparable research has been described for the CSF-B-B. The main goal of this dissertation was to begin to assess the role of mast cell products on the chief component of the CSF-B-B, the arachnoid mater. Specifically, the hypothesis that mast cell products modulate arachnoid function through receptor mediated second messenger system regulation was postulated. Initially, the light and electron microscopic features of the porcine spinal meninges generally and the arachnoid mater specifically were characterized and found to be similar to those of other species and CNS regions. In addition, mast cells were found to be present in the meninges where their product could affect the arachnoid mater. To study the effects of the selected mast products on the arachnoid mater, arachnoid cells were isolated and cultured. Morphologic, immunohistochemical, and physiological studies confirmed the cultured cells were arachnid cells and that they were capable of developing attributes of a barrier membrane in vitro, (e.g. tight junctions, increased transcellular resistance). The effects of mast cell products on arachnoid cells were then assessed biochemically. Arachnoid cells were found to produce cyclic adenosine monophosphate (cAMP) in response to forskolin and prostaglandin D2 (PGD2). Histamine inhibited both forskolin and PGD2 stimulated production of cAMP. Additionally, arachnoid cells produced inositol phosphates (IP) in response to carbachol and histamine via muscarinic and H1-histamine receptors respectively. Since histamine and PGD2 are produced and released by activated mast cells, and since cAMP and IP levels are known to modulate cellular barrier systems, it is concluded that meningeal mast cells and their products may regulate or modulate permeability of the CSF-B-B. An understanding of the specific biochemical actions of mast cell products on the arachnoid may ultimately aid in the understanding of many physiologic and pathologic processes involving the arachnoid such as hydrocephalus, subarachnoid and subdural hemorrhages, cerebral edema, meningitis, and meningiomas.Item Brain Derived Neurotrophic Factor Regulates Müller Cell Survival via MAPK and PI3K Pathways(2003-05-01) Taylor, Sara A.; Agarwal, Neeraj; Wordinger, Robert J.; Pang, Iok-HouTaylor, Sara A., Brain Derived Neurotrophic Factor Regulates Müller Cell Survival via MAPK and PI3K Pathways. Master of Science (Biomedical Sciences), January, 2003, 112 pp., 4 tables, 39 illustrations, bibliography, 68 titles. Purpose: Glutamate has been implicated in many pathologies affecting the Central Nervous System including those in the retina, but the exact nature of the role of glutamate in neuronal degeneration remains unclear. In the retina. Müller cells are resistant to glutamate insults that are normally toxic to other cells of the retina, however the molecular and biochemical mechanisms that control their death or survival are not well understood. We used a series of pharmacological inhibitors and molecular biology agents on cultured Müller cells to dissect two key signaling pathways normally involved in cell survival, the Mitogen Activated Protein Kinase – Extracellularly Regulated Kinase (MAPK(ERK) pathway and the Phosphatidylinositide 3 Kinase (PI3K) pathway. Since preliminary data in our laboratory showed that Müller cells upregulate their secretion of neurotrophins including Brain Derived Growth Factor (BDNF) in response to glutamate treatment, we also examined the effect of BDNF on the activation of these two signaling pathways. Methods: Early passaged Müller cells were treated with various concentrations (5 nM -50 μM) of inhibitions of the MAPK(ERK) pathway (GW5074, U0126, and PD98059) or with various concentrations (1-50 μM) of inhibitors of the PI3K pathway (LY294002 or Akt inhibitor) in the presence and absence of 50 ng/ml of BDNF for 24 hours. These experiments were repeated in Müller cells transfected with either NFκB or Bc12 DNA. Cell cultures were then analyzed for surviving cells with an MTS/PMS assay, a colorametric method for determining the number of viable cells in a proliferation assay. Results: The MAPK (ERK) inhibitors PD98059 and GW5074 both resulted in decrease in Müller cell survival. PD98059 did not decrease Müller cell survival until concentrations were high enough to suppress ERK2 phosphorylation. Müller cells transfected with NFκB or Bc12 DNA were able to resist treatment with concentrations of PD98059 that reduced cell number in untransfected cells. The PI3K inhibitor LY294002 also resulted in significant decreases in Müller cell survival in both untransfected cells and cells transfected with NFκB or Bc12 DNA. Treatment with an inhibitor farther down in the PI3K pathway, Akt inhibitor, did not significantly decrease Müller cell survival. Finally, BDNF was not able to increase cell survival in Müller cells treated with PD98059 or U0126, although it did increase the survival of cells treated wit GW5074. BDNF was also able to reverse the decrease in cell survival caused by LY294002 in both untransfected Müller cells or Müller cells transfected with NFκB or Bc12 DNA. Conclusions: Our data shows that Mitogen Activated Protein Kinase – Extracellularly Regulated Kinase (MAPK(ERK) and Phosphatidylinositide 3 Kinase (PI3K) are both essential for Müller cell survival. There is modulation between the pathways and they may interconnected far upstream at a protein previously associated with only the MAPK(ERK) pathway. These results are consistent with a role for both pathways in Müller cell survival.Item Cell line authentication and contamination assessment for human cell cultures(2015-05-01) Ormos, Andrea; Arthur J. Eisenberg; Rhonda Roby; John V. PlanzCell line authentication is an essential step in ensuring the integrity and reproducibility of biomedical research. The major contaminants in cell cultures are fungi, viruses, bacteria and contamination from other cell lines of the same or different species. Contaminants alter the physiology and properties of cells, compromising the results of experiments. In this study, an improved multiplex assay was developed, detecting mycoplasma and mouse cell line contamination, while performing DNA typing. The assay was tested on cell cultures, the reproducibility of the assay was verified, sample collection and procedures were optimized and limit of detection for contaminants were determined. A survey was conducted to assess the interest in an in-house cell line authentication and contamination assessment service.Item Changes in Mammalian Chromatin Structure as a Function of Protein-Poly(ADP-Ribosyl)ation by Endonuclease Digestion(2004-06-01) Perez-Lamigueiro, Maria A.; Alvarez, Rafael; Das, Hriday K.; Basu, AlakanandaPerez-Lamiguerio, Maria A., Changes in Mammalian Chromatin Structure as a Function of Protein-poly(ADP-ribosyl)ation by Endonuclease Digestion. Master of Science (Biochemistry and Molecular Biology), June 2004. 66 pages, 12 illustrations, Bibliography, 45 titles. Mammalian chromatin was exposed to either Deoxyribonuclease I or Micrococcal Nuclease digestion as a function of time of incubation and enzyme concentration. Endonuclease enzymatic reactions were stopped with EDTA. Samples were run in 1.5% agarose gels and the oligonucleosomal electrophoretic migration patterns compared. Endonuclease experiments were carried out with rat liver chromatin pre-incubated in the presence or absence of 200 μM βNAD+. A solution of 1.0 mM benzamide was used to stop enzymatic modification. The electrophoretic observations demonstrated a faster and increased degradation of chromatin when proteins were poly(ADP-ribosyl)ated prior to digestion. These results support the hypothesis that that the covalent poly(ADP-ribosyl)ation of chromatin proteins, particularly histones, induces a more relaxed structure, rendering chromatin more sensitive to endonuclease digestion.Item Characterization and Activity of Endothelin Converting Enzyme-1 in Human Non-Pigmented Ciliary Epithelial Cells(1999-01-01) Finkley, Alvin; Thomas Yorio; S. Dan Dimitrijevich; Victoria J. RudickFinkley, Alvin, Characterization and Activity of Endothelin Converting Enzyme-1 in Human Non-Pigmented Ciliary Epithelial Cells. Master of Science (Biomedical Sciences). Endothelins (ETs) are potent vasoactive peptides, that are present in many ocular tissues including the ciliary epithelium where active ET-1 is produced from the precursor Big ET-1 by a membrane-bound metalloprotease, endothelin-converting enzyme (ECE). Although the role of ocular ET’s are uncertain, ETs have been shown to lower the intraocular pressure. In the current study, ET-1 and Big-ET-1 were detected in SV-40 transformed human ciliary epithelial (HNPE) cells by immunofluorescence suggesting the presence of ECE activity. The presence of ECE was confirmed by Western blotting using polyclonal antibodies against ECE-1 which detected a 124 KDa protein in the membrane fraction and not in the cytosol. Further characterization of the enzymatic activity of ECE (conversion of Big ET-1 to ET-1) was performed using a novel assay involving 121I-Big ET-1 (substrate; 2fmloe) and polyclonal antibodies specific for Big ET-1. Mean ECE-1 activity (expressed as the ratio of 121^1-ET-1 produced to the total 125^I-Big ET-1 incubated X 100) was measured and corresponded to: 26% (0.5 3±0.02 fmole, 1 hr), 63% (1.26±0.07 fmole, 3hr) and 66% (1.33±0.11 fmole, 24 hr) compared to blank controls at 13% (0.25±0.03 fmole). Thiorphan (2mM), an inhibitor of ECE, abolished ECE-1 activity. These results suggest that ECE-1 is localized in HNPE cells and is essential for the production of ET-1. The physiological importance of the proteolytic processing by ECE-1 in ocular tissue may reflect on how ET regulates intraocular pressure. Key Words: endothelin converting enzyme-1; endothelin-1; Big endothelin-1; ciliary epithelium; aqueous humor dynamics; intraocular pressure, Western blotting, ECE-1Item Characterization of a Novel Extracellular Superoxide Dismutase Allele Discovered in Mouse Models of Atherosclerosis(2004-07-01) Pierce, Anson; Dory, Lad; Easom, Robert; Basu, AlakanandaAnson Pierce, Characterization of a Novel Extracellular Superoxide Dismutase Allele Discovered in Mouse Models of Atherosclerosis. Doctor of Philosophy (Biochemistry and Molecular Biology), July 2004, 128 pp., 3 tables, 22 illustrations, references, 230 titles. Many diseases display some involvement with oxidative mechanisms and could potentially benefit from antioxidant therapy designed to restore the balance between reductive and oxidative factors. Data presented in this dissertation explore and establish the protective effect hyperbaric oxygen (HBO) has on the development of atherosclerosis, an oxidation-driven inflammatory disease mediated through low-density lipoproteins in the vasculature. Atherosclerosis in the apolipoprotein E-/- (apoE-/-) mouse is drastically reduced after 10 weeks of HBO treatment. Macrophages in HBO treated mice have an increased antioxidant capacity and reduced ability to generate oxidants. From this work, a new polymorphism of a key antioxidant enzyme, extracellular superoxide dismutase (ecSOD), is identified and characterized in mice. The new polymorphism is termed the “short” allele, and has the potential to alter the regulation of ecSOD mRNA and protein, as well as enzyme activity. Examination of its effect on the ecSOD phenotype in mice shows dramatic changes in enzyme levels and activity. In the plasma compartment ecSOD activity and mass are elevated, and indicate based on heparin injection studies that a change in ecSOD distribution results in tissues of mice expressing the short allele. Systematic examination of ecSOD in tissues of mice shows that its distribution is altered such that it is more accessible to heparin; this is most evident in the liver and kidney of mice expressing the short allele. The finding that HBO is protective against atherosclerosis highlights a potentially promising approach to treatment for this devastating disease, sheds light on the role oxidative processes play in atherosclerosis, and identifies potential targets for antioxidant therapy. This study also shows for the first time that two alleles for a major antioxidant enzyme exist in mice that display markedly different effects on the ecSOD phenotype, a finding that underlines the importance of genetic homogeneity in mouse models and adds to our knowledge concerning the role antioxidants play in human health and disease.Item Characterization of a Novel Receptor CS1 in Human Lymphocytes; Studies in Natural Killer Cells and B-Lymphocytes(2005-06-01) Lee, Jae Kyung; Porunelloor Mathew; Ming-Chi Wu; Hriday DasThe purpose of this study was to investigate the roles of CS1 on human lymphocytes. The molecular and functional characterization of CS1 receptor in the natural killer (NK) cells and B lymphocytes was investigated. CS1 (CRACC, novel Ly9) is a novel member of the CD2 family receptor expressed on natural killer (NK), T cells, activated Bcells and dendritic cells. To examine the existence of isoform of CS1, library from NK cells was screened based on wild type of CS1 (CS1-L). A splice variant form of CS1 (CS1-S), which lacks immunoreceptor tyrosine-based switch motifs (ITSMs) in cytoplasmic domain, was identified. To demonstrate the function of CS1 on human NK cells, transfectants that stably express each isoform were generated. CS1-L was able to mediate redirect cytotoxicity of P815 target cells as well as intracellular calcium influx in the presence of monoclonal antibody against CS1 suggesting that CS1-L is an activating receptor. CS1-S showed no effect on the cytolytic function and calcium influx suggesting that CS1-L and CS1-S may differentially regulate human NK cell functions. Although CS1 was also cloned from cDNA library of human B-lymphocytes as well as of NK cells, very little is known regarding its biology on human B-lymphocytes. Here I investigated the expressions and functions of CS1 in human B cells. Human B cells expresses only CS1-L isoform and the levels of CS1 expression are upregulated after activation in vitro. Importantly, monoclonal antibody of CS1 (1G10 mAb) strongly enhances proliferation of both freshly isolated and activated B cells. The enhanced proliferation effects of CS1 were most prominent on B cells activated by anti-CD40 mAbs and/or IL-4. Human cytokine microarray results indicated CS1 enhanced mRNA transcripts of fms-line tyrosine kinase 3 ligand, lymphotoxin A, tumor necrosis factor, and IL-14 which are related with mostly growth promoting activity. These results suggest that autorine cytokines might be the mediators for the function of CS1 on B cell in which it can induce proliferation of activated B cells. This study suggests that CS1 plays important role in human NK cells and B-lymphocytes.Item Characterization of IL-17A-Secreting CD8 T Cells(2008-12-01) Lee, Suheung; Harlan Jones; Porunellor Mathew; Peter KoulenIL-17A-secreting CD4 T cells (Th17 cells) have been demonstrated to play pivotal roles in modulating immune responses during various types to infectious and autoimmune diseases. While 1L-17A secreting CD8 T cells have been detected in numerous disease models, much less is known about them. In this thesis, the differentiation conditions and effector functions of IL-17A-secreting CD8 T cells have been examined. In order to differentiate naïve CD8 T cells into IL-17A secretors, TGF-β, IL-6, and neutralization of IFN-γ are required as in Th17 cells. IL-17A-secreting CD8 T cells produce the effector cytokines, IL-17A, IL-17F and IL-22, but do not produce granzyme B, implicating the lack of cytotoxicity. Furthermore, IL-17A-secreting CD8 T cells can respond to exogenous cytokines without a cognate antigen, suggesting that they can act in an innate fashion. Collectively, IL-17A-secreting CD8 T cells possess the same effector functions as Th17 cells, and thus may play as significant roles in various diseases at Th17 cells.Item Characterization of Recombinant Lecithin: Cholesterol Acyltransferase, Secreted by a Human Lung Cell Line (1069-111) and by Pichia Pastoris Yeast Cells(2004-05-01) Tchedre, Kissaou T.; Caffrey, James L.; Harris, Ben G.; Wu, Ming-ChiTchedre, Kissaou T., Characterization of Recombinant Lecithin: Cholesterol Acyltransferase, Secreted by a Human Lung Cell Line (1069-111) and by Pichia pastoris Yeast Cells (Biomedical Sciences), May, 2004, Lecithin: cholesterol acyltransferase (LCAT) is a key enzyme in mammalian lipoprotein metabolism. Associated with the surface of high-density lipoproteins (HDL), LCAT contributes to the homeostasis of circulating free and esterified cholesterol via the reverse cholesterol transport pathway. The purpose of these studies was to characterize a recombinant form of LCAT, secreted by a human lung cell line (Beta gene 1069/111) and to evaluate a new expression system for LCAT using transformed Pichia pastoris cells. A human lung cell line (Beta gene 1069/111), transfected with pBIISK (Stratagene)+ vector was used as the source of recombinant (rLCAT) for the first stage of characterization studies. Human lung cells were expanded in Dulbecco’s minimal essential medium (DMEM) supplemented with 10% fetal bovine serum for the expression of the recombinant LCAT. At 80 – 90% confluency, the medium was changed to a serum free preparation and the flasks were incubated for 48 hrs at 37°C to facilitate the secretion of the enzyme. Beta gene (1069/111) LCAT was purified from the conditioned medium using phenyl sepharose chromatography. The purified enzyme was characterized according to: carbohydrate composition, and enzyme kinetic parameters. The enzymatic characteristics, of the human lung cell line LCAT had similar Km and Vmax values to other LCAT preparations, isolated from other expression systems and human plasma. Deglycosylation reduced the molecular weight of the enzyme from about 67,000 to about 43,000 suggesting a carbohydrate component of 25-32% of the enzyme’s total mass. Detailed analysis of the carbohydrate structures revealed N-glycan structures in a complex pattern of sialylated and fucosylated tri and tetra-antennary glycosides (8). In addition to the Beta gene expression, a Pichia pastoris yeast expression system was also developed consisting of human LCAT cDNA cloned into pPICZαA vector along with a removable amino-terminal polyhistidine tag. The Pichia pastoris cells were transformed with a vector containing the LCAT gene cDNA and transformants were selected on agar plates containing zeocine (100μg/ml). Polymerase chain reaction (PCR) and reverse transcription polymerase chain reaction (RT-PCR) were used to confirm the correct integration of the LCAT gene cDNA into the pPICZαA vector. The recombinant LCAT produced by the yeast cultures was purified by Talon affinity chromatography, taking advantage of the removable histidine tag. The enzymatic activity was determined using proteoliposome vesicles. The Yeast expression system yielded ~18 mg of enzyme protein/500 ml and thus may provide an appropriate enzyme source for characterization studies via NMR analysis and x-ray crystallography.Item Characterization of the Bradykinn Receptor in Human Corneal Epithelium(1997-08-01) Wiernas, Terry Kirkham; Michael W. Martin; Glenn Dillon; Michael ForsterWiernas, Terry Kirkham, Characterization of the Bradykinin Receptor in Human Corneal Epithelium. Doctor of Philosophy (Biomedical Sciences), August, 1997, 255 pp., 5 tables, 39 figures, references, 137 titles. Bradykinin (BK) is a well-established mediator of inflammation. High levels of BK in human tears following ocular allergic provocation led to the hypothesis that BK receptors may exist on the corneal epithelium and could play a role in corneal inflammation and/or wound healing, in addition to other functions. To test this hypothesis, human corneal epithelial cells were cultured and used to conduct a series of studies to evaluate and characterize the BK receptor. Due to the limited supply and high cost of primary human corneal epithelial (P-CEPI) cells, in addition to the fact that these cells do not divide and proliferate over more than a few passages, SV40 virus-immortalized human CEPI cells (CEPI-17-CL4) were used as a model system. Extensive studies confirmed that the immortalized cells faithfully represented the primary cells. This study demonstrated the presence of BK receptors on corneal epithelial cells for the first time. The receptors were characterized as the B2 subtype and were found to be represented by an apparent single binding site. Furthermore, stimulation of these receptors was found to elicit concentration-dependent increases in both inositol phosphates, via activation of phospholipase C, and intracellular calcium mobilization. The rank order affinity of BK and its analogs as determined by binding assays was found to correlate well with the rank order potency of BK and its analogs in evoking the latter functional responses, which were blocked by two B2-receptor selective antagonists. A significant, concentration-dependent stimulation of [3H]thymidine uptake in CEPI cell DNA was elicited by BK which suggests a potential mitogenic effect of BK and a role in corneal wound healing. BK did not significantly affect the release of three pro-inflammatory cytokines, prostaglandin E2 or matrix metalloproteinase-1, and seemed to have an inhibitory effect on the release of tumor necrosis factor α. In conclusion, these studies have confirmed that CEPI-17-CL4 cells represent a good in vitro model of human corneal epithelium and have contributed to a better understanding of the ocular effects of BK and characterization of its receptor within the cornea.Item Characterization of the Role of PKN in TGF-Beta 1-Mediated Cell Cycle Regulation of Vascular Smooth Muscle Cells(2005-12-01) Su, Chang; Neeraj Agarwal; Glenn Dillon; Robert MalletChang Su, Characterization of the role of PKN in TGF-beta-1 induced cell cycle inhibition in vascular smooth muscle cells. Doctor of Philosophy (Biomedical Sciences), November 2005, 173 pp, 2 tables, 34 illustrations, 225 references. Mature vascular smooth muscle cells (VSMCs) are unique in that they can switch between proliferative and differentiated phenotypes. Aberrant proliferation of VSMC is regarded as a central feature in vascular diseases such as atherosclerosis and restenosis following balloon angioplasty. Transforming growth factor-β1 (TGF-β1) is known to inhibit smooth muscle cell progression; however, the signaling pathway(s) through which this is accomplished is poorly understood. Entry into mitosis in dividing VSMCs is triggered by Cdc2/cyclin B1 complex, which is tightly controlled by phosphatase Cdc25C that dephosphorylates tyrosine-15 and threonine-14 on Cdc2 at onset of mitosis. A serine/threonine protein kinase, PKN, was recently reported to inhibit Cdc25C activity. PKN has been identified as a downstream target for TGF-β1 signaling in VSMCs. Therefore we hypothesize that PKN mediates TGF-β1-delayed cell cycle progression by inhibiting Cdc25C. In this study, TGF-β1 is shown to delay G2/M phase progression timing in PAC-1 VSMCs. This effect is blocked by pretreatment of cells with either HA1077 of Y-27632, two pharmacological inhibitors of PKN, as well as by reduced expression of PKN by RNA interference (RNAi). Oscillation of PKN activity temporally correlates with G2/M phase progression. Co-immunoprecipitation suggests that Cdc25C and PKN physically associate with each other. Immunocytochemistry demonstrate that PKN and Cdc25C co-localize in the nuclei and peri-nuclear region of only dividing (M phase) cells but not in the interphase cells. Additionally, PKN phosphorylates Cdc25C in PAC-1 cell cultures. Finally, TGF-β1-induced delay of Cdc2 activation is abolished by pretreating the cells with Y-27632. These data suggest that PKN inhibits G2/M progression by directly binding to Cdc25C and inhibiting its activity by phosphorylation. In addition to the PKN-Cdc25C signaling pathway, TGF-β1 strongly induces the transcriptional activity of the Smad-dependent enhancer in PAC-1 cells. This effect is attenuated by blocking PKN function by either chemical inhibitors or RNAi. Active forms of MKK3/6 alone are sufficient to increase the Smad enhancer activity, and co-expression of dominant negative MKK3/6 decreases TGF-β1-induced activation of the Smad enhancer. Lastly, the Smad reporter activity induced by TGF-β1 is also significantly attenuated by SB203580, a highly specific pharmacological inhibitor for p38 MAPK. These data demonstrate a novel mechanism of PKN-MKK3/6-p38 MAPK cascade to cross talk with the Smad pathway in PAC-1 VSMCs. Taken together, findings presented in this dissertation identify components of important intracellular signaling pathways through which TGF-β1 activates PKN to inhibit proliferation and promote differentiation of SMCs. Augmenting PKN-Cdc25C-Cdc2 signaling may provide a potential therapeutic approach to counter abnormal VSMC proliferation, prevent the clinical consequences of atherosclerosis and improve outcomes after angioplasty.Item Conformational Properties of Circulating and Recombinant Forms of Human Plasma Lecithin Cholesterol ACYL Transferase(1995-06-01) Sundarrajan, Geetha; Walter McConathySundarrajan, Geetha, Conformational properties of circulating and recombinant forms of human plasma LCAT Master of Science (Biomedical Sciences), June, 1995, 69pp., 3 tables, 18 figures, 47 references. The relationship between enzymatic activity and conformational properties of the circulating and recombinant forms of human plasma LCAT were examined in the native and denatured states. The two denaturing agents used in this study were guanidine hydrochloride and heat. These studies led to the following conclusions: (1) Although the alpha helical content of desialylated recombinant LCAT (d-LCAT) is comparable to that of the other two forms of the enzyme (p-LCAT and r-LCAT), the desialylation of LCAT is associated with an increase in the beta sheet and a decrease in beta turn content. (2) The presence of sialic acids, in addition, seems to influence the local environments of aromatic amino acid residues. (3) From the denaturation and renaturation studies with guanidine hydrochloride and heat, it appears that the N-glycan structures of p-PCAT and r-LCAT may contribute differentially to the conformational stability of the enzyme. (4) The alpha helical structure of LCAT may not be involved in maintaining the active conformation of the enzyme.Item Conformational Transitions in Myosin Subfragment-1(2000-08-01) Ushakov, Dmitriy S.; Julian Borejdo; Oleg Andreev; Tony RomeoUshakov, Dmitriy S., Conformational transitions in myosin subfragment-1. Doctor of Philosophy (Biochemistry), June 2000, 72 pp., 7 tables, 19 illustrations, bibliography: 139 titles. The contraction of muscles is driven by ATP-dependent interaction of actin and myosin filaments. It has been recently shown that the regulatory domain (RD) of smooth muscle myosin, containing both the regulatory and essential light chains, exists in different orientations depending on the nucleotide bound to the myosin ATPase site. However, this could not be detected in skeletal muscle myosin, and therefore it is still not known whether it is the RD or the change in the myosin motor domain (MD) that is responsible for the force production. To investigate this, we used chemical cross-linking to analyze the binding of myosin subfragment-1 (S1) to F-actin in the presence of various adenine nucleotides. We found that ADP causes the reorientation of S1 with respect to F-actin, but only at physiological molar ratio of S1 to actin. The result can be simply explained by the two-state model of S1 binding to F-actin proposed earlier, in which S1 binds to one (state 1) or two (state 2) actin monomers, depending on the saturation of the filaments with S1. This suggests that the change in the orientation of RD could be a mere consequence of the conformational change in the MD. To investigate the changes in the RD further, we used a fluorescence anisotropy of an external fluorophore attached to a specific cysteine residue of the protein. To facilitate experiments, a tag of 6 histidines was genetically introduced at the C-terminus of LC1. The recombinant LC1 was labeled with rhodamine at the cysteine 178 near the C-terminus, and exchanged into free S1 or in muscle fibers. The fluorescence anisotropy showed that the LC1 becomes more immobilized in the presence of ATP compared to the rigor state. The fact that ATP increases immobilization of LC1 suggests that the conformational changes take place in the RD of S1 during the ATP hydrolysis. The ordering of the LC1 could be due to the ATP-induced closure of the cleft between a small β-sheet on LC1 (Cys178-Met145) and a flexible loop on the catalytic domain (Arg18-Arg24). From presented evidences, we conclude that the conformational transitions in both the MD and RD of S1 contribute to the power stroke.Item Detection of Androgen Receptors by Flow Cytometry(2008-05-01) Dutta, Mayurika; McClain, Robert; Singh, Meharvan; Hall, StanDutta, Mayurika, ‘Detection of androgen receptors by Flow Cytometry’. Internship Practicum report, Biotechnology, May 2008, 80 pp., 1 table, 18 figures. The use of androgen therapy is expanding given the documented potential benefits like increasing bone mineral density, muscle mass and strength. Androgen therapy also has potential risks including increasing the likelihood of prostate cancer and cardiovascular disease. So, we need a way to differentiate those who are likely to be benefitted by the therapy and those that are not. Data from Dr. Meharvan Singh’s lab has shown that activation of intracellular androgen receptors triggers cell survival pathways, while activation of the membrane androgen receptor suppresses cytoprotective pathways, and thus promotes cell death. We propose to develop a diagnostic kit that measures the relative ratio of intracellular androgen receptors and membrane androgen receptors, which is predicted to gauge relative risks or benefits associated with androgen therapy.Item Distribution of Poly(ADP-ribose) Glycohydrolase in Different Functional Domains of the Cell Nucleus(1996-08-01) Pacheco-Rodriguez, Gustavo; Rafael Alvarez; Robert Easom; Ming-Chi WuPacheco-Rodriguez, Gustavo, Distribution of Poly(ADP-ribose) Glycohydrolase in Different Functional Domains of the Cell Nucleus. Doctor of Philosophy (Biomedical Sciences), August, 1996, 147 pp, 3 tables, 44 illustrations, bibliography, 138 titles. In this study, the distributor poly(ADP-ribose) glycohydrolase (PARG) in different subdomains of the cell nucleus and the role of non-covalent interactions of poly(ADP-ribose) with nuclear proteins have been characterized. An assay that allows the simultaneous determination of specific non-covalent interactions of poly (ADP-ribose) with nuclear proteins as well as PARG activity by high resolution polyacrylamide gel electrophoresis was developed. This method was made possible by the enzymatic synthesis of (ADP-ribose)2-70 at 10 μM NAD+ with purified poly(ADP ribose) polymerase (PARP). Either purified or nuclear-associated PARG degraded poly(ADP-ribose) biphasically. Nuclei were fractioned into functional domains namely, chromatin, nuclear matrix and nuclear envelope. These domains were characterized biochemically by their protein composition and by electron microscopy. PARG activity was identified mainly with chromatin and the nuclear matrix. Interestingly, PARG activity was also associated with the nuclear envelope. Thus, the poly(ADP-ribosyl)ation pathway is regulated topologically. It was further determined that poly(ADP-ribose) interacts non-covalently with purified histone proteins or proteins in the nuclear environment. In addition, the nuclear matrix proteins also interacted non-covalently with poly(ADP-ribose). These non-covalent interactions appear to regulate the catabolism of poly(ADP-ribose) via a catabolite intermediate constituted of a [protein][poly(ADP-ribose)] complex. The affinity of the nuclear associated protein responsible for triggering the degradation of poly(ADP-ribose) correlates with the affinity of histone H4 for ADP-ribose chains of 20 residues or more. The findings of this research stresses that : a) poly (ADP-ribose) is catabolized by PARG in vivo; b) PARG is associated with chromatin, nuclear matrix and the nuclear envelope; c) the degradation of poly(ADP-ribose) is dependent on its non-covalent interactions with nuclear proteins; and d) histone H4 appears to be responsible for triggering the catabolism of poly(ADP-ribose).Item Effects of the Pleiotropic Gene csrA on Glycogen Metabolism in Escherichia Coli(1995-06-01) Yang, Honghui; Ming-Chi Wu; Wayne NicholsonYang, Honghui, Effects of the pleiotropic gene csrA on glycogen metabolism in Escherichia coli. Master of Science (Biomedical Sciences), June, 1995, 78 pp., 3 tables, 17 illustrations, bibliography, 59 titles. The csrA gene negatively regulates the expression of four genes glgB, glgC, glgA and glgS involved in glycogen synthesis. It also negatively regulates glgY, which encodes the enzyme glycogen phoshorylase involved in glycogen degradation, but no effect was observed on the glycogen debranching enzyme in this pathway. In addition, csrA exhibits a positive effect on the glycolytic enzyme triosephosphate isomerase. No significant effects were observed on the expression of two genes (zwf & gnd) participating in the pentose phosphate pathway. In vitro expression of glgB, glgC and glgA was specifically inhibited by cell extracts containing the csrA gene product (CsrA). This study provides evidence that csrA encodes an important regulator of intermediary carbon metabolism in Escherichia coli.Item EGCG and Its Role in Prostate Cancer Angiogenesis(2005-05-01) Thomas, Rusha; Porunelloor Mathew; Ming-Chi Wu; Dan DimitrijevichThomas, Rusha, EGCG and its role in prostate cancer angiogenesis. Master of Science (Biochemistry and Molecular Biology), May 2005, 47 pages, 14 illustrations, reference list, 44 titles. Hypoxia inducible factor-1 (HIF-1)-mediated upregulation of vascular endothelial growth factor (VEGF) has been implicated in angiogenesis associated with malignancies. HIF-1 consists of a constitutively expressed HIF-1β subunit, and a hypoxia-inducible HIF-1α subunit. Hypoxic induction of HIF-1α correlates with increased transcriptional activation of its downstream target genes, including VEGF. Epidemiologic and laboratory studies indicate that green tea has cancer preventive activity which has been attributed to its polyphenol components, the major one being epigallocatechin gallate (EGCG). This study investigated the effect of EGCG on normoxic VEGF expression in PC-3ML human prostate cancer cells. In contrast to previous studies where EGCG inhibited VEGF expression in breast and colon cancer cell lines, our results demonstrated that EGCG has the ability to upregulate HIF-1α transcription factor via inhibition of prolyl hydroxylation and subsequent von Hippel-Lindau protein interaction. HIF-1α upregulation by EGCG led to increased VEGF promoter activity and protein expression.