1,721,028 research outputs found
Editorial: Disparate roles of mitochondria in cell survival and cell death: new insight from the CNS
Full text linkThe author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Approaches to Cloning and Identification of the Ligand for Natural Cytotoxicity Receptor NKp44
No full textHorton, Nathan C., Approaches to Cloning and Identification of the Ligand for the Natural Cytotoxicity Receptor, NKp44. Masters of Science (Microbiology & Immunology), July 2008, 64 pp., 22 illustrations, 37 titles. Natural Killer (NK) cells represent a specialized lymphoid population that mediate innate immune responses against tumor or virally infected cells. NK cell cytotoxicity is regulated by inhibitory and activating receptors. Activating receptors include the Natural Cytotoxicity Receptors (NCRs), 2B4, and NKG2D. The NCRs play a key role in recognition and killing of tumor cells and include the receptors NKp30, NKp46, and NKp44. The ligands for the NCRs are not yet known. NKp44 is of particular interest because it is only expressed on activated NK cells, and is implicated in increased cytotoxicity and HIV infection. To identify and clone the ligand for NKp44, a recombinant fusion protein containing the extracellular domain of NKp44 was constructed and used to identify a cell line, DB, expressing a ligand for NKp44. A directional complimentary DNA (cDNA) library was constructed from this cell line and screened by mammalian expression cloning, resulting in the isolation of several putative cDNA clones of NKp44 ligands
Endothelin-1 Mediated Regulation of Extracellular Matrix Collagens- A Role in Pathology of Primary Open Angle Glaucoma
Full text linkEndothelin -1 Mediated Regulation of Extracellular Matrix Collagens –A role in Pathology of Primary Open Angle Glaucoma. Vidhya R. Rao, Doctor of Philosophy. (Pharmacology and Neuroscience), November, 2007, 157 pp., 3 tables, 18 figures. Summary. Primary Open Angle Glaucoma (POAG) is a progressive optic neuropathy characterized by loss of retinal ganglion cells, optic nerve degeneration and characteristic extracellular matrix (ECM) remodeling of the optic nerve head. An increase in collagen type I and VI is observed at the level of lamina cribosa (LC), a distinct connective tissue region of optic nerve in POAG subjects. Extensive ECM remodeling with enhanced collagen deposition observed in POAG is consistent with the pathology of fibrosis. Mechanisms contributing to ECM remodeling in POAG is not known. Endothelin-1(ET-1), a potent vaso-active peptide plays a key role in glaucoma pathology. Intra-vitreal administration of ET-1 in animal models results in optic neuropathy, RGC apoptosis, axonal transport block and ONA activation. An upregulation of ET-1 and ETB receptors is observed in glaucomatous LC and animal models of glaucoma and ET-1 mediated detrimental effects in POAG appears to be mediated by ETB receptors. ET-1 initiatives and maintains enhanced collagen synthesis and deposition in various tissues under pathological conditions and is recognized as a potent profibrotic factor. In the present study we hypothesized that ET-1 increases extracellular matrix collagen deposition in lamina cribrosa and this change in ECM contributes to optic nerve fibrosis. We have demonstrated that cells of lamina cribrose (LC) cells, express functional ETA and ETB receptors. ET-1 increases intracellular calcium mobilization via ETA receptors and increases NO release by mechanisms involving both ETA and ETB receptors. Consistent with POAG pathology we have observed an upregulation ETB receptors in LC cells in response to chronic treatment with ET-1. LC cells also express prepro-ET-1, the primary gene transcript of ET-1. We have demonstrated for the first time that ET-1 exerts its profibrotic effects by enhancing collagen type I and type VI mRNA, protein synthesis, deposition and secretion in LC cells. ET-1 enhanced collagen deposition in LC cells appears to involve both ETA and ETB receptors, as both of the receptor antagonist, individually inhibit ET-1 mediated collagen synthesis. We have demonstrated that ET-1 also exerts its profibrotic effects in vivo by enhancing collagen deposition in rat optic nerve head. We have also observed an apparent decrease in ET-1 mediated collagen VI deposition in optic nerve heads of ETB deficient transgenic rats suggesting that ET-1 mediated collagen VI synthesis involves ETB receptor activation. In conclusion, endothlein-1 stimulates collagen synthesis and deposition both in vitro in LC cells as well as in vivo at the level of rat optic nerve head. ET-1 mediated increase in collage synthesis at the level of optic nerve head could render a fibrotic mechanism that contributes to the progression of POAG
Role of Glucocorticoid Receptor β in Glucocorticoid-Induced Ocular Hypertension
No full textJiang, Ming, Role of Glucocorticoid Receptor β in Glucocorticoid-Induced Ocular Hypertension, Master of Science. (Biomedical Sciences). Purpose: Previous studies from our laboratory have shown that glaucomatous trabecular meshwork ™ cells have a lower expression of glucocorticoid beta (GRβ) compared to normal TM cells. Overexpression of glucocorticoid receptor β was found to attenuate glucocorticoid responsiveness in glaucomatous TM cells. The purpose of this study was to determine if downregulating GRβ expression could increase glucocorticoid responsiveness in cultured transformed normal trabecular meshwork cells (NTM5 cells) and primary trabecular meshwork cell lines derived from normal individuals. Methods: siRNA oligonucleotide sequences specific for GRβ were designed, cloned into expression vectors and sequenced. TM cells were transfected with different siRNA constructs for GRβ, while a scrambled sequence served as a negative control. Immunoblot analyses were carried out in the transfected TM cells to determine knockdown of GRβ expression. In another set of experiments TM cells were transfected with either a GRβ siRNA construct or an empty vector (control) and co-transfected with a GRE-luciferase reporter and a SV40 promoter-β galactosidase construct to normalize for efficiency of transfection. Promoter-reporter assays were carried out to determine the effect of GRβ knockdown on glucocorticoid-mediated luciferase reporter activity. Results: Using MetafecteneTM rpo as the transfection reagent for siRNA, an appreciable 50% to 90% decrease in GRβ protein expression was observed 72 hours post-transfection in three GRβ siRNA constructs transfected in NTM5 cells, compared to the scrambled sequence transfected cells. NTM5 cells transfected with the empty vector (control) showed a 3.5 fold increase in luciferase activity after dexamethasone treatment, which was further increased (4 to 5 fold) by knocking down GRβ expression using a siRNA construct specific for GRβ. A similar trend was found using GRβ-siRNA#3 to transient knockdown GRβ in four primary TM cell lines – NTM210-05, NTM486-04, NTM174-04, and NTM153-00, respectively. To investigate to glucocorticoid responsiveness in cells permanently transfected for knockdown of GRβ, we made 6 clones from NTM5 cells. There were 10 to 20 fold induction in luciferase activity in GRβ siRNA stably transfected NTM5 cells, following glucocorticoid administration, respectively. Conclusion: In this study, using RNAi(s) which is specific for GRβ, we decreased GRβ expression in vitro in several different cell lines. Using luciferase assays it was found that the glucocorticoid responsiveness after knockdown of GRβ in vitro in trabecular meshwork cells was significantly enhanced. Decreased GRβ expression significantly increased glucocorticoid responsiveness not only in normal transformed human trabecular meshwork cells (NTM5 cells), but also in four primary trabecular meshwork ™ cell lines derived from normal individuals. These results further support the notion that GRβ negatively regulates responsiveness in TM cells. Keywords: glaucoma, glucocorticoid, glucocorticoid receptor beta, trabecular meshwor
Serum Deprivation Induces Apoptosis of Retinal Ganglion Cells Utilizing Mitochondrial Signaling Pathways
Full text linkCharles, Irma E., Serum Deprivation Induced Apoptosis of Retinal Ganglion Cells Utilizing Mitochondrial Signaling Pathways. Master of Science (Biomedical Sciences), December 2003, 90 pp., 10 illustrations. Apoptosis is the genetically regulated death of retinal ganglion cells (RGC) in which there is a blockade of retrograde transport. This blockade results in the loss of neurotrophic growth factors that are essential for the survival of the RGCs. This study uses several different techniques to determine mechanisms underlying apoptosis in rat RGCs deprived of growth factors. An established line of transformed RGC was subjected to serum deprivation for 2-6 days and compared to RGC cells maintained in 10% FBS to study the cellular changes that occur as a result of the treatments. The results show that serum deprivation for 48 hours resulted in a 50% cell loss due to apoptosis. Apoptotic death was associated with activation of caspases 3, 8, and 9 along with increased levels of Bax and death receptors 3 & 4. These results indicate that serum deprivation results in RGC death via mitochondrial and also extrinsic pathways
Studies of Checkpoint Responses Caused by Endogenous Oxidative DNA Damage in DNA Repair Deficient Saccharomyces Cerevisiae
No full textPawar, Vaibhav., Studies of checkpoint responses caused by endogenous oxidative DNA damage in DNA repair deficient Saccharomyces cerevisiae. Doctor of Philosophy (Biomedical Sciences), December 2008, 163 pp., 21 illustrations, 189 references. In this dissertation project, I aimed to study checkpoint response of stationary phase yeast to DNA damage caused by basal oxidative stress. My study was focused on the regulation of Rad53 phosphorylation in different repair deficient strains to yeast. Rad53 plays decisive roles in cell cycle progression, cell death and transcriptional regulation of repair proteins to a plethora of DNA insults, including oxidative DNA damage. Rad53 activity is upregulated by phosphorylation, generating Rad53 species of various degrees of phosphorylation. I have measured steady state levels of Rad53 phosphorlyation by western blotting following SDS-polyacrylamide gel electrophoresis at different intervals in stationary phase, in various mutant backgrounds. To address the possible contribution of different repair pathways to endogenous DNA damage, I utilized two different sets of DNA repair deficient strains such as those deficient in Base excision repair (BER) and nucleotide excision repair (NER), and other set was deficient in Ku protein and NER. Interestingly, in both BERNER and Yku70rad4 strains, Rad53 phosphorylation was evident in stationary phase that is after 2 days, 4 days and 6 days but not in logarithmic phase. This covalent modification disappears after phosphatase treatment. This Rad53 modification was absent in their respective rho0 mutants, which lack mitochondrial DNA, indicating involvement of mitochondrial ROS in this checkpoint response. We analyzed mutants of different checkpoint proteins for Rad53 phosphorylation. Exclusive involvement of Rad17, Rad50 and Mec1 kinase in Rad53 phosphorylation strongly suggests processed DNA double strand breaks as critical lesions in BERNER cells. Analysis of Yku70 and NER deficient strain showed involvement of ssDNA, which is most likely at telomeres. This study consents with the model of unrepaired oxidative base damage, which can accelerate the appearance of single stranded DNA in the vicinity of double strand breaks (DSBs) or at telomeres
Quality Assurance Training: Will a New Training Intervention Improve Data Collection of the Texas Emergency Medicine Research Associate Program (TEMRAP)?
No full textIntroduction: Data collection is vital for the success of a clinical research project. The purpose of this practicum was to address the inadequate data collection by the Texas Emergency Medicine Research Associate Program (TEMRAP) research associates (RAs). The primary goal was to incorporate a more efficient training method to reduce the RAs' error rate in the documentation. The secondary aim of this experiment was to determine if RAs' knowledge of clinical research studies and/or their self-confidence when enrolling a patient had an effect on quality of data collection and if these variables could be improved by a new training method. Methods: A randomized clinical trial was used to evaluate the efficacy of simulated clinical research enrollment training as a teaching and/or learning method to reduce the error rate in submitted research packets by RAs. The returning RAs were randomized into an intervention group with new training (simulations) and a control group with current training (didactic presentations). A self-confidence survey and a knowledge questionnaire were completed by RAs pre/post-training and one-month follow-up. Quality of data collection was measured by comparing the error rates of data collection in completed clinical research enrollment packets submitted by the RAs in the intervention group versus the control group. Results: Results showed no statistically significant difference in the level of knowledge, confidence or error rates between the patient enrollment simulation (intervention) group and the didactic presentations (control) group after their respective training (p [greater than] .05). However, there was a statistically significant increase in knowledge and confidence post-training in patient simulations group. A significant association was present between confidence and error rate but not between knowledge and error rate for research associates in either training group. Conclusion: Clinical simulation training was not a significantly more effecting training method compared to current TEMRAP didactic presentation training. Even though knowledge and confidence did increase post-training there was no significant difference between the two types of training. Future experiments should explore the possibility of combining the two types of training and observing other potential variables affecting the quality of data, such as research associates' motivation. Additionally, the need for a larger sample size and enrolling participants with no prior research experience should be explored for significant results
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